Re: [zfs-discuss] what have you been buying for slog and l2arc?
On 08/ 4/12 09:50 PM, Eugen Leitl wrote: On Fri, Aug 03, 2012 at 08:39:55PM -0500, Bob Friesenhahn wrote: Extreme write IOPS claims in consumer SSDs are normally based on large write caches which can lose even more data if there is a power failure. Intel 311 with a good UPS would seem to be a reasonable tradeoff. The 313 series looks like a consumer price SLC drive aimed at the recent trend in windows cache drives. Should be worth a look. -- Ian. ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
On 08/06/2012 10:06 PM, Erik Trimble wrote: Honestly, I don't think this last point can be emphasized enough. SSDs of all flavors and manufacturers have a track record of *consistently* lying when returning from a cache flush command. There might exist somebody out there who actually does it across all products, but I've tested and used enough of the variety (both Consumer and Enterprise) to NOT trust any SSD that tells you it actually flushed out its local cache. Anyone know if Seagate pulsar's lie about cache flush's? http://www.seagate.com/files/www-content/product-content/pulsar-fam/pulsar/pulsar-2/en-us/docs/pulsar2-ds1728-3-1202us.pdf Karl CONFIDENTIALITY NOTICE: This communication (including all attachments) is confidential and is intended for the use of the named addressee(s) only and may contain information that is private, confidential, privileged, and exempt from disclosure under law. All rights to privilege are expressly claimed and reserved and are not waived. Any use, dissemination, distribution, copying or disclosure of this message and any attachments, in whole or in part, by anyone other than the intended recipient(s) is strictly prohibited. If you have received this communication in error, please notify the sender immediately, delete this communication from all data storage devices and destroy all hard copies.___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
It depends on the model. Consumer models are less likely to immediately flush. My understanding that this is done in part to do some write coalescing and reduce the number of P/E cycles. Enterprise models should either flush, or contain a super capacitor that provides enough power for the drive to complete writing any date in its buffer. My Home Fusion SSD runs on banana peels and eggshells and uses a Flux Capacitor. I've never had a failure. ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
On 08/07/2012 02:18 AM, Christopher George wrote: I mean this as constructive criticism, not as angry bickering. I totally respect you guys doing your own thing. Thanks, I'll try my best to address your comments... Thanks for your kind reply, though there are some points I'd like to address, if that's okay. *) Increased capacity for high-volume applications. We do have a select number of customers striping two X1s for a total capacity of 8GB, but for a majority of our customers 4GB is perfect. Increasing capacity obviously increases the cost, so we wanted the baseline capacity to reflect a solution to most but not every need. Certainly, for most uses this isn't an issue. I just threw that in there, considering how cheap DRAM and flash is nowadays and how easy it is to create disk pools which push 2GB/s in write thoughput, I was hoping you guys would be keeping pace with that (getting 4GB of sync writes in the txg commit window can be tough, but not unthinkable). In any case, simply dismissing it by saying that simply get two, you are effectively doubling my slog costs which, considering the recommended practice is to get a slog mirror, would mean that I have to get 4 X1's. That's $8k in list prices and 8 full-height PCI-e slots wasted (seeing as how an X1 is wider than the standard PCI-e card). Not many systems can do that (that's why I said solder the DRAM and go low-profile). *) Remove the requirement to have an external UPS (couple of supercaps? microbattery?) Done! We will be formally introducing an optional DDRdrive SuperCap PowerPack at the upcoming OpenStorage Summit. Great! Though I suppose that will inflate the price even further (seeing as you used the word optional). *) Use cheaper MLC flash to lower cost - it's only written to in case of a power outage, anyway so lower write cycles aren't an issue and modern MLC is almost as fast as SLC at sequential IO (within 10% usually). We will be staying with SLC not only for performance but longevity/reliability. Check out the specifications (ie erase/program cycles and required ECC) for a modern 20 nm MLC chip and then let me know if this is where you *really* want to cut costs :) MLC is so much cheaper that you can simply slap on twice as much and use the rest for ECC, mirroring or simply overprovisioning sectors. The common practice to extending the lifecycle of MLC is by short-stroking it, i.e. using only a fraction of the capacity. E.g. a 40GB MLC unit with 5-10k cycles per cell can be turned into a 4GB unit (with the controller providing wear leveling) with effectively 50-100k cycles (that's SLC land) for about a hundred bucks. Also, since I'm mirroring it already with ZFS checksums to provide integrity checking, your argument simply doesn't hold up. Oh and don't count on Illumos missing support for SCSI Unmap or SATA TRIM forever. Work is underway to rectify this situation. *) PCI Express 3.0 interface (perhaps even x4) Our product is FPGA based and the PCIe capability is the biggest factor in determining component cost. When we introduced the X1, the FPGA cost *alone* to support just PCIe Gen2 x8 was greater than the current street price of the DDRdrive X1. I always had a bit of an issue with non-hotswappable storage systems. What if an X1 slog dies? I need to power the machine down, open it up, take out the slog, put it another one and power it back up. Since ZFS has slog removal support, there's no reason to go for non-hotpluggable slogs anyway. What about 6G SAS? Dual ported you could push around 12Gbit/s of bandwidth to/from the device, way more than the current 250MB/s, and get hotplug support in there too. *) At least updated benchmarks your site to compare against modern flash-based competition (not the Intel X25-E, which is seriously stone age by now...) I completely agree we need to refresh the website, not even the photos are representative of our shipping product (we now offer VLP DIMMs). We are engineers first and foremost, but an updated website is in the works. In the mean time, we have benchmarked against both the Intel 320/710 in my OpenStorage Summit 2011 presentation which can be found at: http://www.ddrdrive.com/zil_rw_revelation.pdf I always had a bit of an issue with your benchmarks. First off, you're only ever doing synthetics. They are very nice, but don't provide much in terms of real-world perspective. Try and compare on price too. Take something like a Dell R720, stick in the equivalent (in terms of cost!) of DRAM SSDs and Flash SSDs (i.e. for X1 you're looking at like 4 Intel 710s) and run some real workloads (database benchmarks, virtualization benchmarks, etc.). Experiment beats theory, every time. *) Lower price, lower price, lower price. I can get 3-4 200GB OCZ Talos-Rs for $2k FFS. That means I could equip my machine with one to two mirrored slogs and nearly 800GB worth of L2ARC for the price of a single X1. I
Re: [zfs-discuss] what have you been buying for slog and l2arc?
On Mon, 6 Aug 2012, Christopher George wrote: I mean this as constructive criticism, not as angry bickering. I totally respect you guys doing your own thing. Thanks, I'll try my best to address your comments... *) At least updated benchmarks your site to compare against modern flash-based competition (not the Intel X25-E, which is seriously stone age by now...) I completely agree we need to refresh the website, not even the photos are representative of our shipping product (we now offer VLP DIMMs). We are engineers first and foremost, but an updated website is in the works. In the mean time, we have benchmarked against both the Intel 320/710 in my OpenStorage Summit 2011 presentation which can be found at: http://www.ddrdrive.com/zil_rw_revelation.pdf Very impressive iops numbers. Although I have some thoughts on the benchmarking method itself. Imho the comparison shouldn't be raw iops numbers on the ddrdrive itself as tested with iometer (it's only 4gb), but real world numbers on a real world pool consisting of spinning disks with ddrdrive acting as zil accelerator. I just introduced an intel 320 120gb as zil accelerator for a simple zpool with two sas disks in raid0 configuration, and it's not as bad as in your presentation. It shows about 50% of the possible nfs ops with the ssd as zil versus no zil (sync=disabled on oi151), and about 6x-8x the performance compared to the pool without any accelerator and sync=standard. The case with no zil is the upper limit one can achieve on a given pool, in my case creation of about 750 small files/sec via nfs. With the ssd it's 380 files/sec (nfs stack is a limiting factor, too). Or about 2400 8k write iops with the ssd vs. 11900 iops with zil disabled, and 250 iops without accelerator (gnu dd with oflag=sync). Not bad at all. This could be just good enough for small businesses and moderate sized pools. Michael -- Michael Hase edition-software GmbH http://edition-software.de ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
On Tue, 7 Aug 2012, Sašo Kiselkov wrote: MLC is so much cheaper that you can simply slap on twice as much and use the rest for ECC, mirroring or simply overprovisioning sectors. The common practice to extending the lifecycle of MLC is by short-stroking it, i.e. using only a fraction of the capacity. E.g. a 40GB MLC unit with 5-10k cycles per cell can be turned into a 4GB unit (with the controller providing wear leveling) with effectively 50-100k cycles (that's SLC land) for about a hundred bucks. Also, since I'm mirroring it already with ZFS checksums to provide integrity checking, your argument simply doesn't hold up. Remember he also said that the current product is based principally on an FPGA. This FPGA must be interfacing directly with the Flash device so it would need to be substantially redesigned to deal with MLC Flash (probably at least an order of magnitude more complex), or else a microcontroller would need to be added to the design, and firmware would handle the substantial complexities. If the Flash device writes slower, then the power has to stay up longer. If the Flash device reads slower, then it takes longer for the drive to come back on line. Quite a lot of product would need to be sold in order to pay for both re-engineering and the cost of running a business. Regardless, continual product re-development is necessary or else it will surely die. Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer,http://www.GraphicsMagick.org/___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
On 08/07/2012 04:08 PM, Bob Friesenhahn wrote: On Tue, 7 Aug 2012, Sašo Kiselkov wrote: MLC is so much cheaper that you can simply slap on twice as much and use the rest for ECC, mirroring or simply overprovisioning sectors. The common practice to extending the lifecycle of MLC is by short-stroking it, i.e. using only a fraction of the capacity. E.g. a 40GB MLC unit with 5-10k cycles per cell can be turned into a 4GB unit (with the controller providing wear leveling) with effectively 50-100k cycles (that's SLC land) for about a hundred bucks. Also, since I'm mirroring it already with ZFS checksums to provide integrity checking, your argument simply doesn't hold up. Remember he also said that the current product is based principally on an FPGA. This FPGA must be interfacing directly with the Flash device so it would need to be substantially redesigned to deal with MLC Flash (probably at least an order of magnitude more complex), or else a microcontroller would need to be added to the design, and firmware would handle the substantial complexities. If the Flash device writes slower, then the power has to stay up longer. If the Flash device reads slower, then it takes longer for the drive to come back on line. Yeah, I know, but then, you can interface with an existing industry-standard flash controller, no need to design your own (reinvent the wheel). The choice of FPGA is good for some things, but flexibility in exchanging components certainly isn't one of them. If I were designing something akin to the X1, I'd go with a generic embedded CPU design (e.g. a PowerPC core) interfacing with standard flash components and running the primary front-end from the chip's on-board DRAM. I mean, just to give you some perspective, for $2k I could build a full computer with 8GB of mirrored ECC DRAM which interfaces via an off-the-shelf 6G SAS HBA (with two 4x wide 6G SAS ports) or perhaps even an InfiniBand adapter with RDMA with the host machine, includes a small SSD in it's SATA bay and a tiny UPS battery to run the whole thing for a few minutes while we write DRAM contents to flash in case of a power outage (the current X1 doesn't even include this in its base design). And that's something I could do with off-the-shelf components for less than $2k (probably a whole lot less) with a production volume of _1_. Quite a lot of product would need to be sold in order to pay for both re-engineering and the cost of running a business. Sure, that's why I said it's David vs. Goliath. However, let's be honest here, the X1 isn't a terribly complex product. It's quite literally a tiny computer with some DRAM and a feature to dump DRAM contents to Flash (and read it back later) in case power fails. That's it. Cheers, -- Saso ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
Very impressive iops numbers. Although I have some thoughts on the benchmarking method itself. Imho the comparison shouldn't be raw iops numbers on the ddrdrive itself as tested with iometer (it's only 4gb), The purpose of the benchmarks presented is to isolate the inherent capability of just the SSD in a simple/synthetic/sustained Iometer 4KB random write test. This test successfully illuminates a critical difference between a Flash only and a DRAM/SLC based SSD. Flash only SSD vendors are *less* than forthright in their marketing when specifying their 4KB random write capability. I am surprised vendors are not called out for marketing FOB (fresh out of the box) results (that even with TRIM support) are not sustainable. Intel was a notable exception until they also introduced SSDs based on SandForce controllers. In the section prior to the benchmarks, titled ZIL Accelerator access pattern random and/or sequential I show an example workload and how it translates to an actual log device's access pattern. It clearly shows a wide (21-71%) spectrum of random write accesses. So before even presenting any Iometer results, I don't believe I indicate or even imply that real world workloads will somehow be 100% 4KB random write based. For the record, I agree with you as they are obviously not! real world numbers on a real world pool consisting of spinning disks with ddrdrive acting as zil accelerator. Benchmarking is frustrating for us also, as what is a real world pool? And if we picked one to benchmark, how relevant would it be to others? 1) number of vdevs (we see anywhere from one to massive) 2) vdev configuration (only mirrored pairs to 12 disk raidz2) 3) HDD type (low rpm green HDDs to SSD only pools) 4) host memory size (we see not enough to 192GB+) 5) number of host CPUs (you get the picture) 6) network connection (1GB to multiple 10GB) 7) number of network ports 8) direct connect to client or through a switch(s) Is the ZFS pool accessed using NFS or iSCSI? What is the client OS? What is the client configuration? What is the workload composition (read/async write/sync write)? What is the workload access pattern (sequential/random)? ... This could be just good enough for small businesses and moderate sized pools. No doubt, we are also very clear on who we target (enterprise customers). The beauty of ZFS is the flexibility of it's implementation. By supporting multiple log device types and configurations it ultimately enables a broad range of performance capabilities! Best regards, Chris -- Christopher George cgeorge at ddrdrive.com http://www.ddrdrive.com ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
Stec ZeusRAM for Slog - it's exensive and small, but it's the best out there. OCZ Talos C for L2ARC. -Original Message- From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-boun...@opensolaris.org] On Behalf Of Bob Friesenhahn Sent: Friday, August 03, 2012 8:40 PM To: Karl Rossing Cc: ZFS filesystem discussion list Subject: Re: [zfs-discuss] what have you been buying for slog and l2arc? On Fri, 3 Aug 2012, Karl Rossing wrote: I'm looking at http://www.intel.com/content/www/us/en/solid-state-drives/solid-state- drives-ssd.html wondering what I should get. Are people getting intel 330's for l2arc and 520's for slog? For the slog, you should look for a SLC technology SSD which saves unwritten data on power failure. In Intel-speak, this is called Enhanced Power Loss Data Protection. I am not running across any Intel SSDs which claim to match these requirements. Extreme write IOPS claims in consumer SSDs are normally based on large write caches which can lose even more data if there is a power failure. Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer,http://www.GraphicsMagick.org/ ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
Are people getting intel 330's for l2arc and 520's for slog? Unfortunately, the Intel 520 does *not* power protect it's on-board volatile cache (unlike the Intel 320/710 SSD). Intel has an eye-opening technology brief, describing the benefits of power-loss data protection at: http://www.intel.com/content/www/us/en/solid-state-drives/ssd-320-series-power-loss-data-protection-brief.html Intel's brief also clears up a prior controversy of what types of data are actually cached, per the brief it's both user and system data! Best regards, Christopher George www.ddrdrive.com *** The Intel 311 (SLC NAND) also fails to support on-board power protection. ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
Unfortunately, the Intel 520 does *not* power protect it's on-board volatile cache (unlike the Intel 320/710 SSD). Intel has an eye-opening technology brief, describing the benefits of power-loss data protection at: http://www.intel.com/content/www/us/en/solid-state-drives/ssd-320-series-power-loss-data-protection-brief.html Intel's brief also clears up a prior controversy of what types of data are actually cached, per the brief it's both user and system data! So you're saying that SSDs don't generally flush data to stable medium when instructed to? So data written before an fsync is not guaranteed to be seen after a power-down? If that -- ignoring cache flush requests -- is the whole reason why SSDs are so fast, I'm glad I haven't got one yet. ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
On Mon, Aug 6, 2012 at 2:15 PM, Stefan Ring stefan...@gmail.com wrote: So you're saying that SSDs don't generally flush data to stable medium when instructed to? So data written before an fsync is not guaranteed to be seen after a power-down? It depends on the model. Consumer models are less likely to immediately flush. My understanding that this is done in part to do some write coalescing and reduce the number of P/E cycles. Enterprise models should either flush, or contain a super capacitor that provides enough power for the drive to complete writing any date in its buffer. If that -- ignoring cache flush requests -- is the whole reason why SSDs are so fast, I'm glad I haven't got one yet. They're fast for random reads and writes because they don't have seek latency. They're fast for sequential IO because they aren't limited by spindle speed. -- Brandon High : bh...@freaks.com ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
On Mon, 6 Aug 2012, Christopher George wrote: Intel's brief also clears up a prior controversy of what types of data are actually cached, per the brief it's both user and system data! I am glad to hear that both user AND system data is stored. That is rather reassuring. :-) Is your DDRDrive product still supported and moving? Is it well supported for Illumos? Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer,http://www.GraphicsMagick.org/ ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
On Mon, 6 Aug 2012, Stefan Ring wrote: Intel's brief also clears up a prior controversy of what types of data are actually cached, per the brief it's both user and system data! So you're saying that SSDs don't generally flush data to stable medium when instructed to? So data written before an fsync is not guaranteed to be seen after a power-down? If that -- ignoring cache flush requests -- is the whole reason why SSDs are so fast, I'm glad I haven't got one yet. Testing has shown that many SSDs do not flush the data prior to claiming that they have done so. The flush request may hasten the time until the next actual cache flush. As far as I am aware, Intel does not sell any enterprise-class SSDs even though they have sold some models with 'E' in the name. True enterprise SSDs can cost 5-10X the price of larger consumer models. A battery-backed RAM cache with Flash backup can be a whole lot faster and still satisfy many users. Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer,http://www.GraphicsMagick.org/ ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
Is your DDRdrive product still supported and moving? Yes, we now exclusively target ZIL acceleration. We will be at the upcoming OpenStorage Summit 2012, and encourage those attending to stop by our booth and say hello :-) http://www.openstoragesummit.org/ Is it well supported for Illumos? Yes! Customers using Illumos derived distros make-up a good portion of our customer base. Thanks, Christopher George www.ddrdrive.com ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
On 08/07/2012 12:12 AM, Christopher George wrote: Is your DDRdrive product still supported and moving? Yes, we now exclusively target ZIL acceleration. We will be at the upcoming OpenStorage Summit 2012, and encourage those attending to stop by our booth and say hello :-) http://www.openstoragesummit.org/ Is it well supported for Illumos? Yes! Customers using Illumos derived distros make-up a good portion of our customer base. How come I haven't seen new products coming from you guys? I mean, the X1 is past 3 years old and some improvements would be sort of expected in that timeframe. Off the top of my head, I'd welcome things such as: *) Increased capacity for high-volume applications. *) Remove the requirement to have an external UPS (couple of supercaps? microbattery?) *) Use cheaper MLC flash to lower cost - it's only written to in case of a power outage, anyway so lower write cycles aren't an issue and modern MLC is almost as fast as SLC at sequential IO (within 10% usually). *) PCI Express 3.0 interface (perhaps even x4) *) Soldered-on DRAM to create a true low-profile card (the current DIMM slots look like a weird dirty hack). *) At least updated benchmarks your site to compare against modern flash-based competition (not the Intel X25-E, which is seriously stone age by now...) *) Lower price, lower price, lower price. I can get 3-4 200GB OCZ Talos-Rs for $2k FFS. That means I could equip my machine with one to two mirrored slogs and nearly 800GB worth of L2ARC for the price of a single X1. I mean this as constructive criticism, not as angry bickering. I totally respect you guys doing your own thing. Cheers, -- Saso ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
I am glad to hear that both user AND system data is stored. That is rather reassuring. :-) I agree! --- [Excerpt from the linked Intel Technology Brief] What Type of Data is Protected: During an unsafe shutdown, firmware routines in the Intel SSD 320 Series respond to power loss interrupt and make sure both user data and system data in the temporary buffers are transferred to the NAND media. --- I was taking user data to indicate actual txg data and system data to mean the SSD's internal meta data... I'm curious, any other interpretations? Thanks, Chris Christopher George cgeorge at ddrdrive.com http://www.ddrdrive.com/ ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
On 8/6/2012 2:53 PM, Bob Friesenhahn wrote: On Mon, 6 Aug 2012, Stefan Ring wrote: Intel's brief also clears up a prior controversy of what types of data are actually cached, per the brief it's both user and system data! So you're saying that SSDs don't generally flush data to stable medium when instructed to? So data written before an fsync is not guaranteed to be seen after a power-down? If that -- ignoring cache flush requests -- is the whole reason why SSDs are so fast, I'm glad I haven't got one yet. Testing has shown that many SSDs do not flush the data prior to claiming that they have done so. The flush request may hasten the time until the next actual cache flush. Honestly, I don't think this last point can be emphasized enough. SSDs of all flavors and manufacturers have a track record of *consistently* lying when returning from a cache flush command. There might exist somebody out there who actually does it across all products, but I've tested and used enough of the variety (both Consumer and Enterprise) to NOT trust any SSD that tells you it actually flushed out its local cache. ALWAYS insist on some form of power protection, whether it be a supercap, battery, or external power-supply. That way, even if they lie to you, you're covered from a power loss. -Erik ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
On Fri, Aug 03, 2012 at 08:39:55PM -0500, Bob Friesenhahn wrote: For the slog, you should look for a SLC technology SSD which saves unwritten data on power failure. In Intel-speak, this is called Enhanced Power Loss Data Protection. I am not running across any Intel SSDs which claim to match these requirements. The http://www.intel.com/content/www/us/en/solid-state-drives/solid-state-drives-710-series.html seems to qualify: Enhanced power-loss data protection. Saves all cached data in the process of being written before the Intel SSD 710 Series shuts down, which helps minimize potential data loss in the event of an unexpected system power loss. Extreme write IOPS claims in consumer SSDs are normally based on large write caches which can lose even more data if there is a power failure. Intel 311 with a good UPS would seem to be a reasonable tradeoff. ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
hi may be check out stec ssd or checkout the service manual of sun zfs appliance service manual to see the read and write ssd in the system regards Sent from my iPad On Aug 3, 2012, at 22:05, Hung-Sheng Tsao (LaoTsao) Ph.D laot...@gmail.com wrote: Intel 311 Series Larsen Creek 20GB 2.5 SATA II SLC Enterprise Solid State Disk SSDSA2VP020G201 Average Rating (12 reviews) Write a Review Sent from my iPad On Aug 3, 2012, at 21:39, Bob Friesenhahn bfrie...@simple.dallas.tx.us wrote: On Fri, 3 Aug 2012, Karl Rossing wrote: I'm looking at http://www.intel.com/content/www/us/en/solid-state-drives/solid-state-drives-ssd.html wondering what I should get. Are people getting intel 330's for l2arc and 520's for slog? For the slog, you should look for a SLC technology SSD which saves unwritten data on power failure. In Intel-speak, this is called Enhanced Power Loss Data Protection. I am not running across any Intel SSDs which claim to match these requirements. Extreme write IOPS claims in consumer SSDs are normally based on large write caches which can lose even more data if there is a power failure. Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer,http://www.GraphicsMagick.org/ ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
On Fri, 3 Aug 2012, Neil Perrin wrote: For the slog, you should look for a SLC technology SSD which saves unwritten data on power failure. In Intel-speak, this is called Enhanced Power Loss Data Protection. I am not running across any Intel SSDs which claim to match these requirements. - That shouldn't be necessary. ZFS flushes the write cache for any device written before returning from the synchronous request to ensure data stability. Yes, but the problem is that the write IOPS go way way down (and device lifetime suffers) if the device is not able to perform write caching. A consumer-grade device advertizing 70K write IOPS is definitely not going to offer anything like that if it actually flushes its cache when requested. A device with a reserve of energy sufficient to write its cache to backing FLASH on power fail will be able to defer cache flush requests. Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer,http://www.GraphicsMagick.org/ ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
On Fri, 3 Aug 2012, Karl Rossing wrote: I'm looking at http://www.intel.com/content/www/us/en/solid-state-drives/solid-state-drives-ssd.html wondering what I should get. Are people getting intel 330's for l2arc and 520's for slog? For the slog, you should look for a SLC technology SSD which saves unwritten data on power failure. In Intel-speak, this is called Enhanced Power Loss Data Protection. I am not running across any Intel SSDs which claim to match these requirements. Extreme write IOPS claims in consumer SSDs are normally based on large write caches which can lose even more data if there is a power failure. Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer,http://www.GraphicsMagick.org/ ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
Intel 311 Series Larsen Creek 20GB 2.5 SATA II SLC Enterprise Solid State Disk SSDSA2VP020G201 Average Rating (12 reviews) Write a Review Sent from my iPad On Aug 3, 2012, at 21:39, Bob Friesenhahn bfrie...@simple.dallas.tx.us wrote: On Fri, 3 Aug 2012, Karl Rossing wrote: I'm looking at http://www.intel.com/content/www/us/en/solid-state-drives/solid-state-drives-ssd.html wondering what I should get. Are people getting intel 330's for l2arc and 520's for slog? For the slog, you should look for a SLC technology SSD which saves unwritten data on power failure. In Intel-speak, this is called Enhanced Power Loss Data Protection. I am not running across any Intel SSDs which claim to match these requirements. Extreme write IOPS claims in consumer SSDs are normally based on large write caches which can lose even more data if there is a power failure. Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer,http://www.GraphicsMagick.org/ ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] what have you been buying for slog and l2arc?
On 08/03/12 19:39, Bob Friesenhahn wrote: On Fri, 3 Aug 2012, Karl Rossing wrote: I'm looking at http://www.intel.com/content/www/us/en/solid-state-drives/solid-state-drives-ssd.html wondering what I should get. Are people getting intel 330's for l2arc and 520's for slog? For the slog, you should look for a SLC technology SSD which saves unwritten data on power failure. In Intel-speak, this is called Enhanced Power Loss Data Protection. I am not running across any Intel SSDs which claim to match these requirements. - That shouldn't be necessary. ZFS flushes the write cache for any device written before returning from the synchronous request to ensure data stability. Extreme write IOPS claims in consumer SSDs are normally based on large write caches which can lose even more data if there is a power failure. Bob ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
