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  1. #1
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    15K rpm SAS disks greater than 146 GB?

    Currently we're using HP servers with 4 hot-swap bays that hold 3.5" Seagate Cheetah 15K RPM SAS disks, which we can get in 300, 450, and 600 GB flavors.

    I'm looking at the HP DL380/385 models which use 2.5" SAS disks. About the only decent 15K RPM SAS disk I've found in 2.5" form is the Seagate Savvio, but it doesn't come any larger than 146 GB.

    Anyone know of another enterprise-class SAS disk that has all of the following attributes: 2.5", 15K RPM, SAS, and at least 300 GB?

    (Please, no 10K RPM or SATA recommendations like the WD Velociraptor. I won't consider anything that's not 15K RPM SAS.)

  2. #2
    The SAS/SFF is not yet available in sizes larger than 146GB @15k.

    The latest news, as of a couple of weeks ago, was entry into the market by a couple of other vendors at 146/15K. So, maybe next year.
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  3. #3
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    Thanks, that confirms what I suspected.

    On the bright side, it gives me an excuse to stick with the 1U chassis. Even though 3.5" is old school, 4 x 600 GB 15K RPM in RAID 1+0 is 1 TB of very fast storage, and the disks are cheap.

    There isn't much point in us going to the 2U chassis with 8 SFF disks until the 2.5" units are available in at least 300 GB. At 8 x 146 GB in RAID 1+0, that's barely over 500 GB of storage-- not nearly enough on a machine with 32 or 64 GB RAM and two quad-core Xeons. I'm not interested in (slower) external storage, given what these servers are used for.

  4. #4
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    Quote Originally Posted by Sekweta View Post
    Thanks, that confirms what I suspected.

    On the bright side, it gives me an excuse to stick with the 1U chassis. Even though 3.5" is old school, 4 x 600 GB 15K RPM in RAID 1+0 is 1 TB of very fast storage, and the disks are cheap.

    There isn't much point in us going to the 2U chassis with 8 SFF disks until the 2.5" units are available in at least 300 GB. At 8 x 146 GB in RAID 1+0, that's barely over 500 GB of storage-- not nearly enough on a machine with 32 or 64 GB RAM and two quad-core Xeons. I'm not interested in (slower) external storage, given what these servers are used for.
    The HP direct-attached storage appliances would use the same controller as the in-built hot-swap bays (just with an external x4 port); these would not be slower. You could use an HP StorageWorks D2000 or MSA 20/60 with 3.5" 15k SAS drives in tandem with smaller capacity SFF drives in the hot-swap bays (for a boot array).

  5. #5
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    We've gone for 8 x 2.5" 10K when we previously went for 6 x 3.5" 15K - the difference in average random access time is very small because the head has to read over a small area, so the lower RPM is largely compensated for, and you'll find very similar performance overall.
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  6. #6
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    If you had to go with the chassis w/ the 2.5" disks, you could think about getting SSDs. There are a decent number of them at 256 gigs with pretty impressive performance.

  7. #7
    Quote Originally Posted by dazmanultra View Post
    We've gone for 8 x 2.5" 10K when we previously went for 6 x 3.5" 15K - the difference in average random access time is very small because the head has to read over a small area, so the lower RPM is largely compensated for, and you'll find very similar performance overall.
    There are also two other factors to consider. Faster seeks because of smaller distance and reduced mass. More spindles to spread the load over. Both of these help.
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  8. #8
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    Yep, external storage tanks are great. Unfortunately, given the specific role of these servers, our primary need is for on-board storage in the 1 TB range, with very fast write capability, fitting within cost constraints that would be blown out by an external disk array.

    We couldn't meet the price-point we have to be at on this particular service, if we had to use external storage. I am a fan of external arrays, though-- we use 12 and 15 disk iSCSI/SATA arrays for all of our backup servers. Dirt cheap, reliable storage.

  9. #9
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    You know you can still order the DL380/385 with 6x LFF (3.5") cage, right? You can just do without SFF bays to get what you need and stay within budget. Granted, it doesn't hold as many drives as an SFF configuration, but 6x 300GB 15k SAS LFF = 1.5TB RAID 5. Or order the second SFF cage for a total of 16x SFF bays. 16x 146GB 15k SAS SFF = 2.19TB RAID 5. That meets your requirements with room to use a drive as hot spare.

  10. #10
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    Quote Originally Posted by Enteligent-Rob View Post
    You know you can still order the DL380/385 with 6x LFF (3.5") cage, right?
    No, I didn't know that. Thanks for the heads up on that one-- that might be quite useful.

    I need storage density of roughly 1 TB per 1U. I was considering the DL380/385 with 8 drive bays until I found I couldn't get anywhere near 2 TB of RAID 1+0 storage with SFF didks. But if there is a 6xLFF option, that would be 1.8 TB using six 600 GB drives. Close enough.


  11. #12
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    Sweet. If WD came out with a 2.5" SAS at 300 GB, hopefully Seagate won't be too far behind with their 15K RPM Savvio.

    I'm still extremely partial to the Seagate Cheetahs because they are downright indestructable, but I know 3.5" is long in the tooth and we can't hold on to yesterday's technology forever.

  12. #13
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    I wonder how much if at all different these drives will be from the current SATA Raptor drives? I haven't had good luck with raptor reliability at all lately.

  13. #14
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    I wouldn't be surprised if they're Veloiraptors, with SAS firmware.

    Re reliability-- did you have problems with Raptor or Velociraptor?

    The old (3.5") Raptors were quick, but unreliable. The new Velociraptors are 2.5", much faster and (supposedly) far more reliable.

    I've used SCSI disks in my own workstation since the mid 90's, but for this new machine I'm using 300 GB Velociraptors and (so far) they've been extremely good performers.

    I would not use them in servers (yet) because of the TLER issues, which tells me even though WD calls the Velociraptors "enterprise" class, they are not quite ready for anything other than desktops.

  14. #15
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    Quote Originally Posted by Sekweta View Post
    I've used SCSI disks in my own workstation since the mid 90's, but for this new machine I'm using 300 GB Velociraptors and (so far) they've been extremely good performers.

    I would not use them in servers (yet) because of the TLER issues, which tells me even though WD calls the Velociraptors "enterprise" class, they are not quite ready for anything other than desktops.
    Granted we don't own the hardware ourselves but we use Softlayer and we had several machines with 300GB Velociraptors in raid-10 and it did not go well. I guess they did not set the TLER properly and over the course of about 4 months we had replaced every single drive because the raid card (Adaptec 5405) dropped the drives. This happened on several machines to not just one. Fixing the TLER setting solved it but that's pretty bad issue to run into. Decided best to use 300GB SAS drives then deal with these raptors any further. Very easy to forget to change the TLER for when you're running in raid.
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  15. #16
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    Quote Originally Posted by tkam View Post
    I wonder how much if at all different these drives will be from the current SATA Raptor drives? I haven't had good luck with raptor reliability at all lately.
    I used a single 150GB WD Raptor in one of my Dell desktops for a while, and it was very quick (access times) compared to a regular SATA drive. The drive lasted for quite a while until it was dropped while sitting out on a desk plugged into a SATA-to-USB adapter.

    However, the difference between SATA (even at 10k) and SAS (especially at 15k) is night and day. The spindle speed helps of course, but the SAS interface is just so much better in many ways. I now use a 146GB 15k SAS Seagate Cheetah in the same desktop and Windows 7 boots in literally seconds. Using six of these drives in RAID with a Dell PERC 5i I routinely get 2GB/sec burst (cached of course, but still).

  16. #17
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    Quote Originally Posted by Sekweta View Post
    Re reliability-- did you have problems with Raptor or Velociraptor?
    The problems I've had have been with the velociraptors, mostly the 300gig version though I've had a handful of the 150gigs die as well.

  17. #18
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    Quote Originally Posted by tkam View Post
    The problems I've had have been with the velociraptors, mostly the 300gig version though I've had a handful of the 150gigs die as well.
    Have the drives failed slowly over time, or were they sudden failures without warning?

  18. #19
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    Just about every failure was without warning.

  19. #20
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    I have three database servers running with 2x 300GB VelociRaptor drives in RAID-1, and they've never had any problems, at least nothing reported by the 3ware card. Granted they've only been up for five months or so, but still.

  20. #21
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    One of the nice things about SAS is how it's brought SCSI pricing down out of the clouds. The price delta between a 300 GB 10K RPM SATA Velociraptor, and a 300 GB 15K RPM SAS Seagate Cheetah, is under $100.

    Although the Velociraptor performs every bit as good as the Cheetah in a single user desktop environment (despite its 33% lower RPM), in a multi-user server environment the 15K Cheetah flat smokes it.

  21. #22
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    Quote Originally Posted by Sekweta View Post
    One of the nice things about SAS is how it's brought SCSI pricing down out of the clouds. The price delta between a 300 GB 10K RPM SATA Velociraptor, and a 300 GB 15K RPM SAS Seagate Cheetah, is under $100.

    Although the Velociraptor performs every bit as good as the Cheetah in a single user desktop environment (despite its 33% lower RPM), in a multi-user server environment the 15K Cheetah flat smokes it.
    Well, the 15K RPM drive costs $100 more. Continue the trend upwards and say that $100 more than the 15K Cheetah buys you a 32GB x25-e which will annihilate the Cheetah in any scenario. Of course, it has a heck of a lot less capacity...

  22. #23
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    Most hard-core server admins will use what has been proven reliable over time. Specific product selection and preferences vary from shop to shop, but in ours it means the top-of-the-line Seagate Cheetahs because you just can't break them.

    SSDs do have my attention, though, and I'm considering doing a small trial in one or two appliance-type servers (our antispam gateways) that don't need much storage capacity, but do need very high reliability.

    I'd just like to see some long-term reliability numbers on the SSD units before I commit to using more of them.
    Last edited by Sekweta; 11-05-2009 at 06:24 PM.

  23. #24
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    Quote Originally Posted by Guspaz View Post
    32GB x25-e which will annihilate the Cheetah in any scenario.
    Including heavy-traffic server environments? (just asking, I haven't read up on them)

    I know that many desktop drives do extremely well in single-user scenarios, but melt when heavy multi-user I/O begins stacking up, even if they support NCQ.

    Interestingly, enterprise-class server disks (such as the Cheetah) are easily matched by the Velociraptor which has a 33% slower spin rate and SATA plumbing, in single-user desktop environments. (which is why my own workstation has Velociraptors-- not because of cost, but because of performance)

    It's all in what the drive has been tuned for.

  24. #25
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    heavy i/o is where SSD's kill traditional hard drives.

  25. #26
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    Quote Originally Posted by tkam View Post
    heavy i/o is where SSD's kill traditional hard drives.
    The more mechanical/moving parts we can remove from systems, the better.

    I just hope SSD reliability pans out. Recently, I read an article about a data recovery company (the ones who extract data from failed hard drives) and much to my surprise, it said a good percentage of the disks they receive are SSDs.

  26. #27
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    The comparison I like to quote is that one single x25-e produces roughly the same IOPS as eighteen (yes, 18) Cheetahs in RAID-0.

  27. #28
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    That's some serious I/O.

  28. #29
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    Quote Originally Posted by Sekweta View Post
    That's some serious I/O.
    Keeping in mind that the throughput is limited; the x25-m is constrained by the fact that it uses SATA2, which is limited to 3gbit (~250MB/s).

    Fusion-IO's products use PCI-e, so they don't suffer that limitation. Their "consumer-level" drive is $900, but they're MLC. Their enterprise units cost oodles more, but you can get SLC up to 320GB (the 640GB model is MLC-only). But... thousands of dollars per drive.

  29. #30
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    Just FYI, the Western Digital S25 disks that were previously mentioned are only 10k RPM disks. They are not 15k which is what the OP was asking for.

    Personally, I have noted very similar performance when comparing 2.5" 10k disks and 3.5" 15k disks. The improvements in random seek times really make a difference on the 2.5" disks. The 3.5" disks will smoke the 2.5's in sustained read/write though, but that's not a typical scenario in most of our servers.
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