Re: [Declude.JunkMail] Raid Controller

[Matt]

You are selling serial ATA short.  Also, I'm not sure if you are mistaking ATA with serial ATA in your reply. It does turn out that there is some logical speculation that SCSI drive manufacturers are treating SATA as their economy server/workstation class, however Western Digital's 10K drive has no in house SCSI alternative.  Tom's did a comparison of that to the Seagate here:     Smart Hard Drives: Seagate Barracuda 7200.7 and Western Digital WD740 Raptor     http://www.tomshardware.com/storage/20040123/index.html I am definitely going the Western Digital route based on what I saw there. Regarding SATA RAID cards, there are two things happening here.  First, 3wave and LSI are both working on full featured versions for SATA, and they are starting to support native command queuing which apparently can speed performance by 1/3, and instead of bridging ATA to SATA on the hard drives, these are now also being made natively now as well.  Here's a press release concerning LSI's upcoming offering:     LSI Logic launches industry's first PCI-X enabled hardware based MegaRAID SATA 300-8X solution     http://www.lsilogic.com/news/product_news/2004_02_17a.html I don't think you can find any fault with that.  Concerning the bus bottleneck, the PCI-X upgrade will take care of that on a capable system. I did some more research though and found the following review of a new approach to RAID from some former Adaptec employees (now owned by Broadcom).  It's a company known as RAIDcore and their performance is at least on par with Adaptec SCSI in the benchmarks on a RAID 0 installation according to Tom's Hardware     RAIDCore Unleashes SATA to Take Out SCSI     http://www.tomshardware.com/storage/20031114/index.html Better yet, the card has 8 independent channels and you can span across controllers among other things.  I plan on buying one of these and doing RAID 50 which will give me redundancy plus speed without having to dedicate a disk to a specific drive.  This is generally cost prohibitive with SCSI.  RAIDCore claims performance of 450 MB/s sustained reads, and 230 MB/s sustained writes using an 8 drive RAID 50 setup.  The total cost for the drives plus the card would run me $1,200 (no hot swap, though that is available, even Intel is coming out with hot swap SATA drive carriages this quarter).  A comparable setup with SCSI RAID 50 would run 3 times the price and might not out perform.     http://www.raidcore.net/RC4000DataSheet_2.pdf The only issue that I see with this is the company is young and this is their first product (though they are backed by Broadcom now), but it looks real hot and you can get an 8 channel card for under $400. If you are wondering about the effect of RAID 50 over just plain RAID 5, here's a nice start:     http://cdfcaf.fnal.gov/doc/cdfnote_5962/node15.html This shows that while performance decreases with RAID 5 as the number of threads increases, RAID 50 maintains it's throughput until around 40-60 read threads before it drops off.  Naturally this would be somewhat unique to each card, but it makes plenty of sense. I believe that SCSI is just a physical interface/transport layer protocol if I'm not mistaken, and all that makes SCSI special is what's connected to it at either end.  SATA is more capable, and SATA II which does 150 MB/s will be replaced by 300 MB/s versions, 600 MB/s versions, and on, but for now, there is no need for even 100 MB/s on one channel in this configuration so that doesn't matter.  It's foolish to think that SATA won't take over the market as soon as they start connecting the good stuff to SATA wires, and it looks like they are starting to do that now. Matt Keith Anderson wrote: My SCSI RAID10 rack has a dedicated "channel" (if you are referring to the physical cable connecting the drive to the adapter card) for each drive in the rack. They don't share cables in high-end systems, either, especially with SCSI/640. Long before you run into bottlenecks at the drive cables, you will run into a bottleneck at the interface between your adapter card and the motherboard. The only advantage to multiple channels comes from a very efficient write-back cache right on the RAID card. Tom is comparing drives that you can buy at a place like CompUSA, isn't he? Budget ATA vs. budget SCSI (The Cheetah). Aside from the hot-swap advantage and a bit more throughput, SCSI just wasn't meant for the CompUSA market. It was intended and best suited for high-end applications. SCSI is also quickly being replaced by fiber channel in the very high-end systems, because fiber channel handles 2Gig throughput. You don't pay a dollar-per-gigabyte to get 2 gigs of throughput. And YES, the drives are much different. These drives are much bigger, much faster, many more platters and heads, and very reliable, and VERY expensive. They go through weeks of intensive testing before they are released for use. If you look at the Seagate models in the low-end consumer market and compare ATA and SCSI in the same lines, you'll find that the hardware behind the PCB is identical. I won't disagree that they overprice the SCSI version of that drive, but there really is a lot more "smarts" in a SCSI drive than ATA. A SCSI device isn't just hard drives, but entire arrays can be interfaced with SCSI, and other device types like scanners, printers, etc. are supported. The main advantage to SCSI is that all SCSI devices must be able to function completely independent of any other device. For example, the SCSI command structure allows you to copy data directly from one drive to another without data going through the adapter. A SCSI device can be disconnected and reconnected at will from its host, and as long as the host wasn't in need of something at that moment, nothing is interrupted. Error handling is just as complex, with the drive itself able to mark bad sectors and relocate data to spare sectors, all without causing any transaction delays. In contrast, ATA is watered down to be simple, cheap and mass reproducable. Very dependent on a host to tell it what to do at any given moment, and if you disconnect it, it's lost from the system until reboot (and possibly damaged). When errors occur on an ATA drive, it has very little smarts to handle it. A failing ATA will drag a system to its knees. Yes, SCSI is an old standard, but many standards are just as old and they are still the best choice today. Look at Ethernet! -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Matt Sent: Wednesday, March 24, 2004 11:07 PM To: [EMAIL PROTECTED] Subject: Re: [Declude.JunkMail] Raid Controller That's the company that I was told about before. I think you might be selling serial ATA short though. First, these cards have a separate bus for each drive, so a 4 port serial ATA RAID card can handle much more than any single drive can push. No issue there. Secondly, I've been reading reviews for over a year now on Tom's hardware that show IDE drives out performing 15K Cheetahs. This wasn't always the case but it appears that there has been a lot of effort in the IDE realm and very little in the SCSI realm. The SCSI protocol is at least a decade old as well and I see no reason why you should just simply keep doubling the bus with that technology when you can pump more data over a simple firewire or USB cable (along with power). The real question though is how well are these drives made in comparison to the SCSI ones. SCSI is of course just the interface and has no effect on the reliability of the drive. It used to be that they just simply engineered the SCSI drives better, but I don't know that this is entirely the case now, or at least if there enough of a difference for it to really matter. The current SATA drives are generally suggested to be better than IDE, but I wouldn't expect for one to be as reliable as a drive that costs 4 times as much if not more. The incremental boost to reliability may also be moot depending on the application. I plan on having two different gateway machines that only do scanning. Redundancy will be achieved with multiple machines each capable of handling 100% of the total mail volume. If one fails, big whoop, replace the bad drive and you're back in business. Cost becomes an issue for a non-corporate entity, and I can afford to dedicate more drives to more distinct tasks with SATA, and therefore I should be able to achieve better performance. The only variable for me that needs consideration is whether or not the current crop of SATA RAID cards are up to the task. I haven't seen any deep reviews comparing say a 3ware card to a LSI card. Please feel free to tear any of this stuff down. I'm about to make some purchases myself and I hate making mistakes when it comes to such investments. Matt [AUTOMATED NOTE: Your mail server [63.147.33.8] is missing a reverse DNS entry. All Internet hosts are required to have a reverse DNS entry. The missing reverse DNS entry will cause your mail to be treated as spam on some servers, such as AOL.] --- [This E-mail was scanned for viruses by Declude Virus (http://www.declude.com)] --- This E-mail came from the Declude.JunkMail mailing list. 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