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7.2k rpm RAID 0 vs. single 15k rpm drive

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June 24, 2008 8:32:07 PM

So, which is faster? The options are...

2 X 500GB 7.2k rpm drives in RAID 0 using motherboard raid controller

or...

1 300GB 15k rpm drive


The reason I ask is that I'm planning a build for image processing and database development. The final setup would probably be 1 X 73GB 15k drive for OS/Programs and 2 X 300GB for string data, or 4 X 500GB 7.2k drives in raid 10 for both the OS/Programs and data. I've been reading performance reviews of 15k drives and raid setups, but can't quite make it come together. I have it in my head that the raid setup will be good in certain situations, but will use up some cpu and there are situations where it's not great. I think the 15k drives match or exceed the raid array, and won't have any of the drawbacks. Any comments would be appreciated!
June 24, 2008 8:50:07 PM

You will have a bid drawback in cost, with the cheapest 15,000 rpm drive at just under $500 each then to throw in the cost of a good SCSI card as well just to use the drive.
June 24, 2008 9:14:35 PM

IMO, grab yourself as many WD Velociraptors as your budget will allow. Put them in raid 5, save one drive for a fail over and that will be pretty killer performance. Databases will benifit more from the higher rpm (low access time) drives rather than throughput. Encoding video files and working with large graphics you will see more benifit in high MB/s transfer rates.

The raptors are 300 dollars for 300GB you get 10K rpm and excellent transfer rates, though they are a little expensive, they are not nearly as expensive as getting off the ground with SAS where you need a controller and SAS drives which pull a huge premium.
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June 24, 2008 9:41:57 PM

As stated above 15k SAS drives have a cost premium although they are not as bad as $500. But I assume you already know what they cost and that you need a controller. Also remember that all 15k drives are not created equal, you will want some that are around 115mb or more sustained transfer.

Cost aside I would take a single 15k drive any day over 2 - 7200 rpm drives in RAID 0. Also remember RAID 0 kills your access times while boosting your throughput.

Here is a little more I copied from the web

SAS vs SATA
SATA devices are uniquely identified by their port number connected to the Host bus adapter while SAS devices are uniquely identified by their World Wide Name (WWN).
Most SAS drives provide Tagged Command Queuing, while most newer SATA drives provide Native Command Queuing, each of which has its pros and cons.
SATA follows the ATA command set and thus only supports hard drives and CD/DVD drives. In theory, SAS also supports numerous other devices including scanners and printers. However, this advantage could also be moot, as most such devices have also found alternative paths via such buses as USB, IEEE 1394 (FireWire), and Ethernet.
SAS hardware allows multipath I/O to devices while SATA (prior to SATA II) does not. Per specification, SATA II makes use of port multipliers to achieve port expansion. Some port multiplier manufacturers have implemented multipath I/O leveraging port multiplier hardware.
SATA is marketed as a general-purpose successor to Parallel ATA and is now common in the consumer market, while the more expensive SAS is marketed for critical server applications.
SAS error recovery and reporting utilize SCSI commands which have more functionality than the ATA SMART commands used by SATA drives.
SAS uses higher signaling voltages (800-1600 mV TX, 275-1600 mV RX) than SATA (400-600 mV TX, 325-600 mV RX). When SAS is mixed with SATA, the SAS drives run at SATA-voltages. One reason for this higher voltage is so SAS may be used in server backplanes.
Because of its higher signaling voltages, SAS can use cables up to 8 m (25 ft) long, SATA is limited to 1 m (3 ft).
    June 25, 2008 8:48:17 AM

    Thanks for the replies! The two setups I mentioned above work out to the same price. Unfortunately I have to go with a vendor that offers a warranty and support (eg. Dell or Lenovo). I know this isn't the most cost effective setup, but I am more interested in speed and I think that 700GB - 1TB will be enough space for me.

    An example of prices...

    *Dell*
    SATA ($1124)
    4 X 500GB @ $281 = $1124
    SAS ($1193)
    1 X 73GB @ $203 = $203
    2 X 300GB @ $445 = $990

    At Dell the SATA hard drive prices are outrageous, and it make SAS drives economically feasible.

    *Lenovo*
    SATA ($600)
    4 X 500GB @ $154 = $600
    SAS ($1091)
    1 X 73GB @ $191 = $191
    2 X 300GB @ $450 = $900

    At Lenovo the prices make more sense, but I have to switch to Xeon processors and ECC memory to get the RAID 10. Here I can still do the SAS drives on my budget and get a system that more then meets my needs, because the SAS system is cheaper.

    I guess the real question is the quality of SAS drives used by these companies. If they have low sustained transfer rates and other qualities then it won't be worth it.
    June 25, 2008 9:05:46 AM

    Call me an old f4rt but..... what are you doing about backups? Would you not have more options with SAS for tape streamers?

    UD.
    June 25, 2008 9:18:03 AM

    If you are manipulating large files, you want them on the fastest drives.
    June 25, 2008 9:23:23 AM

    UncleDave said:
    Call me an old f4rt but..... what are you doing about backups? Would you not have more options with SAS for tape streamers?

    UD.



    I will be backing up to a server. And if being sensible makes you an old fart then so am I.
    June 25, 2008 10:19:53 AM

    rozar said:
    As stated above 15k SAS drives have a cost premium although they are not as bad as $500. But I assume you already know what they cost and that you need a controller. Also remember that all 15k drives are not created equal, you will want some that are around 115mb or more sustained transfer.

    Cost aside I would take a single 15k drive any day over 2 - 7200 rpm drives in RAID 0. Also remember RAID 0 kills your access times while boosting your throughput.

    Here is a little more I copied from the web

    SAS vs SATA
    SATA devices are uniquely identified by their port number connected to the Host bus adapter while SAS devices are uniquely identified by their World Wide Name (WWN).
    Most SAS drives provide Tagged Command Queuing, while most newer SATA drives provide Native Command Queuing, each of which has its pros and cons.
    SATA follows the ATA command set and thus only supports hard drives and CD/DVD drives. In theory, SAS also supports numerous other devices including scanners and printers. However, this advantage could also be moot, as most such devices have also found alternative paths via such buses as USB, IEEE 1394 (FireWire), and Ethernet.
    SAS hardware allows multipath I/O to devices while SATA (prior to SATA II) does not. Per specification, SATA II makes use of port multipliers to achieve port expansion. Some port multiplier manufacturers have implemented multipath I/O leveraging port multiplier hardware.
    SATA is marketed as a general-purpose successor to Parallel ATA and is now common in the consumer market, while the more expensive SAS is marketed for critical server applications.
    SAS error recovery and reporting utilize SCSI commands which have more functionality than the ATA SMART commands used by SATA drives.
    SAS uses higher signaling voltages (800-1600 mV TX, 275-1600 mV RX) than SATA (400-600 mV TX, 325-600 mV RX). When SAS is mixed with SATA, the SAS drives run at SATA-voltages. One reason for this higher voltage is so SAS may be used in server backplanes.
    Because of its higher signaling voltages, SAS can use cables up to 8 m (25 ft) long, SATA is limited to 1 m (3 ft).


  • I was able to find information on the Lenovo SAS 15k SAS drives and they come in at about 90MB peak sustained transfer. I couldn't find any information on the Dell SAS drives. Dell sells three different brands of 15k 300GB SAS drives (Dell, Fujitsu, and Seagate), and I'm sure the Precision Workstation I was looking at comes with the Dell brand ones with low specs. In searching for the drives I managed to find an awesome thread that is related to this one. I searched with many different keywords yesterday for this exact topic, and it figures that after I post I find something with keywords I wouldn't think would work. I read it once and I'm still not sure which route to go, but when I do I'll post back here with some highlights.

    http://www.hardforum.com/showthread.php?t=1267259
    June 25, 2008 2:18:25 PM

    The SAS drives I use, Seagate 15k.5 drives, are the 115MB a sec or greater drives. I also have a Hitachi 15K drive that is the 90MB or so speed. So it does make a difference. If I were you I would use Seagate unless you can determine that the drive you are buying is 115MB or better.

    Good information in that link, and alot of guys who really like Raptors :-) I had 2 Raptors in RAID 0 when I moved to the SAS drive. BTW if I really liked RAID 0 I would just use 2 SAS drives. But you do take the access time hit.

    Another thing to consider is the controller, What controller will you use? If you are not sure or have not bought one yet look at the Adaptec 5 series before you buy. They are very fast. Just make sure your case has air flow where the controller is.

    June 25, 2008 2:32:15 PM

    You know the bad thing is we are right around the corner from SSD drives being the choice for many people. Right now cost is still high but they are really nice for speed (except for writing small files). Intel is even showing really nice write speed even with small files but you cant buy those yet. I have a few small SSD drives I am testing with but as soon as I get a 64GB I may switch that to my boot drive and use the SAS drive for apps and unimportant storage. Getting way off the deep end :-) I may also use another small SSD just for my pagefile but thats after prices come down.

    Drives are still the slowest thing in our systems................
    June 27, 2008 7:06:28 AM

    Here are some benchies of the seagate 15k SAS drive. These are 3.5in drives.

    Seagate http://www.storagereview.com/ST3300655LW.sr?page=0%2C1

    Here is a head to head comparison of the Seagate SAS vs the VelociRaptor. http://www.storagereview.com/php/benchmark/suite_v4.php?typeID=10&testbedID=4&osID=6&raidconfigID=1&numDrives=1&devID_0=321&devID_1=360&devCnt=2

    Nothing touches the raptor in the 2.5in space for $300. The Savio's are slightly quicker but have lower throughput and cost about double for half the storage space.
    June 27, 2008 9:48:46 AM

    Sarcastic said:

    Nothing touches the raptor in the 2.5in space for $300. The Savio's are slightly quicker but have lower throughput and cost about double for half the storage space.


    It's funny because I stumbled upon the Storage Review website and their velociraptor review the other day, and have pretty much decided on 3 velociraptors (no raid). I have to order the computer with a small drive and add the velociraptors later (1 for OS/Programs, and the other 2 for data), and as long as there is wiring for the 4 drives I think I'm set. Access time is important for the one program I'll be using and throughput is important for the other, and I think the cost/performance/GB ratio of the velociraptors hits the spot.
    June 27, 2008 12:27:53 PM

    Sarcastic said:
    Here are some benchies of the seagate 15k SAS drive. These are 3.5in drives.



    Here is a head to head comparison of the Seagate SAS vs the VelociRaptor. http://www.storagereview.com/php/benchmark/suite_v4.php?typeID=10&testbedID=4&osID=6&raidconfigID=1&numDrives=1&devID_0=321&devID_1=360&devCnt=2




    That comparison is from a SCSI drive although I dont believe SAS would be a ton faster but maybe a little bit. Ont thing though is that recent SAS controllers are better then SCSI. Im trying to get a new Raptor right now for testing to see for myself how fast it is.

    Where I think WD kinda screwed up is the format of the new Raptor. You cant use it in hot swap enclosures, you cant use it in notebooks, you cant even use in servers that use 2.5 inch drives. The only application is discretely connected fixed mount locations. (mostly non-enterprise) Great for desktop though.
    !