Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-24 Thread Bob Friesenhahn
On Fri, 23 Oct 2009, Eric D. Mudama wrote: I don't believe the above statement is correct. According to anandtech who asked Intel: http://www.anandtech.com/cpuchipsets/intel/showdoc.aspx?i=3403p=10 the DRAM doesn't hold user data. The article claims that data goes through an internal 256KB

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-24 Thread Bob Friesenhahn
On Sat, 24 Oct 2009, Bob Friesenhahn wrote: Is solaris incapable of issuing a SATA command FLUSH CACHE EXT? It issues one for each update to the intent log. I should mention that FLASH SSDs without a capacitor/battery-backed cache flush (like the X25-E) are likely to get burned out pretty

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-23 Thread Eric D. Mudama
On Tue, Oct 20 at 22:24, Frédéric VANNIERE wrote: You can't use the Intel X25-E because it has a 32 or 64 MB volatile cache that can't be disabled neither flushed by ZFS. I don't believe the above statement is correct. According to anandtech who asked Intel:

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-22 Thread Edward Ned Harvey
Replacing failed disks is easy when PERC is doing the RAID. Just remove the failed drive and replace with a good one, and the PERC will rebuild automatically. Sorry, not correct. When you replace a failed drive, the perc card doesn't know for certain that the new drive you're adding is meant

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-22 Thread Edward Ned Harvey
The Intel specified random write IOPS are with the cache enabled and without cache flushing. They also carefully only use a limited span of the device, which fits most perfectly with how the device is built. How do you know this? This sounds much more detailed than any average person could

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-22 Thread Ross
Actually, I think this is a case of crossed wires. This issue was reported a while back on a news site for the X25-M G2. Somebody pointed out that these devices have 8GB of cache, which is exactly the dataset size they use for the iops figures. The X25-E datasheet however states that while

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-22 Thread Bob Friesenhahn
On Thu, 22 Oct 2009, Marc Bevand wrote: Bob Friesenhahn bfriesen at simple.dallas.tx.us writes: For random write I/O, caching improves I/O latency not sustained I/O throughput (which is what random write IOPS usually refer to). So Intel can't cheat with caching. However they can cheat by

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-22 Thread Meilicke, Scott
Interesting. We must have different setups with our PERCs. Mine have always auto rebuilt. -- Scott Meilicke On Oct 22, 2009, at 6:14 AM, Edward Ned Harvey sola...@nedharvey.com wrote: Replacing failed disks is easy when PERC is doing the RAID. Just remove the failed drive and replace

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-21 Thread Marc Bevand
Bob Friesenhahn bfriesen at simple.dallas.tx.us writes: [...] X25-E's write cache is volatile), the X25-E has been found to offer a bit more than 1000 write IOPS. I think this is incorrect. On the paper the X25-E offers 3300 random write 4kB IOPS (and Intel is known to be very conservative

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-21 Thread Tristan Ball
What makes you say that the X25-E's cache can't be disabled or flushed? The net seems to be full of references to people who are disabling the cache, or flushing it frequently, and then complaining about the performance! T Frédéric VANNIERE wrote: The ZIL is a write-only log that is only

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-21 Thread Meilicke, Scott
Thank you Bob and Richard. I will go with A, as it also keeps things simple. One physical device per pool. -Scott On 10/20/09 6:46 PM, Bob Friesenhahn bfrie...@simple.dallas.tx.us wrote: On Tue, 20 Oct 2009, Richard Elling wrote: The ZIL device will never require more space than RAM. In

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-21 Thread Meilicke, Scott
Thanks Ed. It sounds like you have run in this mode? No issues with the perc? -- Scott Meilicke On Oct 20, 2009, at 9:59 PM, Edward Ned Harvey sola...@nedharvey.com wrote: System: Dell 2950 16G RAM 16 1.5T SATA disks in a SAS chassis hanging off of an LSI 3801e, no extra drive slots, a

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-21 Thread Edward Ned Harvey
Thanks Ed. It sounds like you have run in this mode? No issues with the perc? You can JBOD with the perc. It might be technically a raid0 or raid1 with a single disk in it, but that would be functionally equivalent to JBOD. The only time I did this was ... I have a Windows server, on

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-21 Thread Scott Meilicke
sigh Thanks Frédéric, that is a very interesting read. So my options as I see them now: 1. Keep the x25-e, and disable the cache. Performance should still be improved, but not by a *whole* like, right? I will google for an expectation, but if anyone knows off the top of their head, I would

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-21 Thread Scott Meilicke
Ed, your comment: If solaris is able to install at all, I would have to acknowledge, I have to shutdown anytime I need to change the Perc configuration, including replacing failed disks. Replacing failed disks is easy when PERC is doing the RAID. Just remove the failed drive and replace with a

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-21 Thread Richard Elling
On Oct 20, 2009, at 10:24 PM, Frédéric VANNIERE wrote: The ZIL is a write-only log that is only read after a power failure. Several GB is large enough for most workloads. You can't use the Intel X25-E because it has a 32 or 64 MB volatile cache that can't be disabled neither flushed by

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-21 Thread Bob Friesenhahn
On Wed, 21 Oct 2009, Marc Bevand wrote: Bob Friesenhahn bfriesen at simple.dallas.tx.us writes: [...] X25-E's write cache is volatile), the X25-E has been found to offer a bit more than 1000 write IOPS. I think this is incorrect. On the paper the X25-E offers 3300 random write 4kB IOPS (and

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-21 Thread David Dyer-Bennet
On Wed, October 21, 2009 12:21, Bob Friesenhahn wrote: Device performance should be specified as a minimum assured level of performance and not as meaningless peak (up to) values. I repeat: peak values are meaningless. Seems a little pessimistic to me. Certainly minimum assured values are

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-21 Thread Bob Friesenhahn
On Wed, 21 Oct 2009, David Dyer-Bennet wrote: Device performance should be specified as a minimum assured level of performance and not as meaningless peak (up to) values. I repeat: peak values are meaningless. Seems a little pessimistic to me. Certainly minimum assured values are the basic

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-21 Thread David Dyer-Bennet
On Wed, October 21, 2009 12:53, Bob Friesenhahn wrote: On Wed, 21 Oct 2009, David Dyer-Bennet wrote: Device performance should be specified as a minimum assured level of performance and not as meaningless peak (up to) values. I repeat: peak values are meaningless. Seems a little

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-21 Thread Paul B. Henson
On Tue, 20 Oct 2009, [UTF-8] Fr??d??ric VANNIERE wrote: You can't use the Intel X25-E because it has a 32 or 64 MB volatile cache that can't be disabled neither flushed by ZFS. Say what? My understanding is that the officially supported Sun SSD for the x4540 is an OEM'd Intel X25-E, so I don't

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-21 Thread Marc Bevand
Bob Friesenhahn bfriesen at simple.dallas.tx.us writes: The Intel specified random write IOPS are with the cache enabled and without cache flushing. For random write I/O, caching improves I/O latency not sustained I/O throughput (which is what random write IOPS usually refer to). So Intel

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-20 Thread Bob Friesenhahn
On Tue, 20 Oct 2009, Scott Meilicke wrote: A. Use all 32G for the ZIL B. Use 8G for the ZIL, 24G for an L2ARC. Any issues with slicing up an SSD like this? C. Use 8G for the ZIL, 16G for an L2ARC, and reserve 8G to be used as a ZIL for the future zpool. Since my future zpool would just be

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-20 Thread Richard Elling
On Oct 20, 2009, at 4:44 PM, Bob Friesenhahn wrote: On Tue, 20 Oct 2009, Scott Meilicke wrote: A. Use all 32G for the ZIL B. Use 8G for the ZIL, 24G for an L2ARC. Any issues with slicing up an SSD like this? C. Use 8G for the ZIL, 16G for an L2ARC, and reserve 8G to be used as a ZIL for

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-20 Thread Bob Friesenhahn
On Tue, 20 Oct 2009, Richard Elling wrote: The ZIL device will never require more space than RAM. In other words, if you only have 16 GB of RAM, you won't need more than that for the separate log. Does the wasted storage space annoy you? :-) What happens if the machine is upgraded to 32GB of

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-20 Thread Edward Ned Harvey
System: Dell 2950 16G RAM 16 1.5T SATA disks in a SAS chassis hanging off of an LSI 3801e, no extra drive slots, a single zpool. svn_124, but with my zpool still running at the 2009.06 version (14). My plan is to put the SSD into an open disk slot on the 2950, but will have to configure

Re: [zfs-discuss] Setting up an SSD ZIL - Need A Reality Check

2009-10-20 Thread Frédéric VANNIERE
The ZIL is a write-only log that is only read after a power failure. Several GB is large enough for most workloads. You can't use the Intel X25-E because it has a 32 or 64 MB volatile cache that can't be disabled neither flushed by ZFS. Imagine your server has a power failure while writing