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  1. #1
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    4 15K SAS RAID 10 vs. 8 7.2K SATAII RAID 10

    Are there any significant difference between 4 15K SAS HD in RAID 10 versus 8 7.2K SATAII HD in RAID 10? I have the same question for 2 15K SAS HD in RAID 1 versus 4 7.2K SATAII HD in RAID 10.

    Thanks!
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  2. #2
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    Anybody can comment?
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  3. #3
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    I would take 8x7.2k SATA-II. The performance difference can be 1.4

  4. #4
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    Average random seek time, the 15K drives will be faster.

    Sustained transfer rate, the bigger number of spindles will win it.

    The former is more useful for web hosting, email, database applications. The latter is more useful for video encoding and moving around very large files.
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  5. #5
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    Quote Originally Posted by gate2vn View Post
    I would take 8x7.2k SATA-II. The performance difference can be 1.4
    Mind explaining me why is the difference so? Thanks!

    Quote Originally Posted by dazmanultra View Post
    Average random seek time, the 15K drives will be faster.

    Sustained transfer rate, the bigger number of spindles will win it.

    The former is more useful for web hosting, email, database applications. The latter is more useful for video encoding and moving around very large files.
    Yes I know that, but do take note the number of drives. I'm sure it makes a difference compared to 1 SAS vs. 1 SATA.
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  6. #6
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    Has anyone tried SSD drives, particularly the intel X25-E?

    If you're looking for performance, that's the direction things are headed.
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  7. #7
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    Quote Originally Posted by LaptopFreak View Post
    Yes I know that, but do take note the number of drives. I'm sure it makes a difference compared to 1 SAS vs. 1 SATA.
    Not sure what more you need to know, he pretty much explained it all.

    Higher RPM means lower seek time, more HDD's in RAID10 means more throughput (MB/s).

    I wonder though, which did you find was cheaper? (Depends on the capacity of the HDD's i'd say.)

  8. #8
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    Quote Originally Posted by XENnode View Post
    Higher RPM means lower seek time, more HDD's in RAID10 means more throughput (MB/s).
    In this case, the 15K SAS drives should have twice the throughput of the 7200 RPM SATA drives, so the two arrays would be comparable in overall throughput.

    As far as IOPS, that can be a bit tricky. The SAS drives have better seek times and more robust queuing, but the SATA configuration has twice as many drives that can seek independently, so again they could be comparable.

    If it were me, I think I would prefer the 4x 15K SAS configuration if capacity isn't a big concern.
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  9. #9
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    Quote Originally Posted by LaptopFreak View Post

    Yes I know that, but do take note the number of drives. I'm sure it makes a difference compared to 1 SAS vs. 1 SATA.
    ...reading his post, it does look like he took note the number of drives.

    Average random seek time, the 15K drives will be faster.

    Sustained transfer rate, the bigger number of spindles will win it.

    The former is more useful for web hosting, email, database applications. The latter is more useful for video encoding and moving around very large files.

  10. #10
    4 SAS Raid-10 VS 8 SATA Raid -10
    same as: 2 SAS Raid-0 VS 4 SATA Raid-0
    same as: 1 SAS vs 2 SATA Raid-0
    ------------------------
    So your qustion maybe can ask like this:
    Is 1 15K SAS HDD is more powerfull than 2 Raid-0 SATA 7200 SATAII enterprise HDD?

    there is 2 key we should pay attention: Continuous transmission speed; IOPS

    ----------------------------
    I do not have 2 7200 Enterprise HDD right now, I have rearch a link, we can see the 2 SATA 7200 HDD in Raid-0 speed is 160MB/s ~ 180MBs average
    ACCESS Time: 7.0ms ~ 12.3ms
    ----------------
    http://www.hardwarecanucks.com/forum...-raid-0-a.html
    ----------------

    and here is ST 15K SAS 300GB
    get average 168.9MB/s (124.8MB/s ~ 186.2MB/s), access time:5.4ms

    ---------------------------------
    http://zigsow.jp/img_page.php?filena...047681.png&a=a

    --------------------------------------

    So we can see, 1 ST 15K SAS in Continuous transmission speed, is almost the same as
    2 SATA 7200RPM HDD in Raid-0 mode.

    but 15K SAS is more fast in track-seeking , That means it can get more IOPS.

    --------------------------------------
    so, I recommend you use 4 15K SAS Raid-10 in your Production environment.(Especially virtualization)

    and SAS HDD is more reliable than SATA.

  11. #11
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    great explain sam

  12. #12
    properly configured, the performance should be pretty close between the two options. If you need more disk space, go sata. If getting half the SAS drives costs less than getting 2x the sata drives, and you don't need the extra space, SAS can make sense. If you really need a lot of performance though, go with SSDs. The samsung ones perform great and in many cases are cheaper per gb than sas these days (unless I've been looking at the wrong sites to get sas prices)
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  13. #13
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    In order to decide what the "best" array is between the options given then you need to understand what it is you need from the array.

    Normally, you are looking for IOPS as opposed to sequential read/write speed.

    http://www.techrepublic.com/blog/dat...age-array/2182 is a great resource when it comes to raid and IOPS. from Personal experience with Enterprise Arrays from Different Manufacturers I can say that the data in this URL is spot on.

    I have experience with medium-sized arrays from different SAN manufacturers and different disk types (speeds) and configurations. I have yet to find an array config that is outside of the ranges from the link. By Medium-sized Arrays, I mean arrays with up to 140 drives per disk group.

    I spent about a week collecting data and doing the maths from real-life results on arrays about a year ago - then had great pleasure in telling a cleint that the $80K they just spent on a SAN was a waste as it would not do what they needed of it in terms of IO performance.

    given the choices, the 15K arrays will provide 5-15% more IOPS than the SATA arrays.

    Given the Info you have presented, if it was me, I would go for 15K disks over 7.2K disks for a couple of reasons. Firstly, the 15K will be marginally faster, Having 1/2 the number of disks will use just over 1/2 the amount of power, and having 1/2 the number of disks assuming the same failure rate, is 1/2 the number of failures.

    The only reason to go for the SATA array would be if the SAS array could not provide the required amount of capacity.

    Now, it also comes down to cost - how much is your 8 port SATA RAID card + your 8 7.2K disks compared to your 4 Port SAS Raid Card and 4 SAS Disks? To be worthwhile, the SATA setup would need to be at least 20% cheaper to be worthwhile.

    I have not done a cost comparision between SAS and SSD's so there is a chance that going SSD might in fact be a cheaper option than SAS per GB of storage.
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  14. #14
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    4 x 15K SAS will be faster and less fail rate , compare to 8 x 7.2K. SSD is faster than the SAS. the more HD, the higher chance of a HD may failed.

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