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RAID sustained R/W computation

Discussion in 'Hardware' started by thrillkiss, Sep 8, 2004.

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  1. thrillkiss

    thrillkiss Thread Starter

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    Hi Guys,

    Please help. Supposed we have 3 80GB HDD with say 20MB/s sustained rate (NOT the burst rate, w/c is normally higher). If we configure the above drive as RAID 0, the total capacity would yield to 240GB, however, how do we compute for the sustained rate of the RAID 0 setup? what are the limiter (if any). If such is the computation, how about other RAID levels?


    thanks and have a brand new day.
     
  2. crjdriver

    crjdriver Moderator

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    First of all, I doubt that you can create a raid 0 with three disks. The way raid 0 works is that block 1 of the data is written to the first disk and block 2 of the data to the second disk; the 3rd block will go to disk 1. So I am not sure what good a third disk in raid 0 will do you.

    You will basically double the read / write speed of the single disk. Using two 80 gig drives will give you an array of 160 gig with double the read / write speed. As an example I use a raid 0 array and get 82 to 84 meg p /s disk speed from the array. A single drive I have connected to the controller gets around 40 meg p /s.

    If you want to setup raid 0, use two disks and have the third for backup / image files.
     
  3. thrillkiss

    thrillkiss Thread Starter

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    Thanks crjdriver, appreciate it buddy. Thought for a while that 2 disk would be the minimum requirement for a RAID 0 setup. Thanks anyway. Noe thats the easy part, supposed I would configure 5 80GB HDD as RAID 5, how would I compute for the sustained rate of the said setup given the same sustained RW rate per drive (20MB)

    thanks again :)
     
  4. thrillkiss

    thrillkiss Thread Starter

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    Thanks crjdriver, appreciate it buddy. Thought for a while that 2 disk would be the minimum requirement for a RAID 0 setup. Thanks anyway. Noe thats the easy part, supposed I would configure 5 80GB HDD as RAID 5, how would I compute for the sustained rate of the said setup given the same sustained RW rate per drive (20MB)

    thanks again :)


     
  5. crjdriver

    crjdriver Moderator

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    It should be double the single drive speed. As to any benchmark to use, I use SiSandra disk or file benchmark. There is a raid array that will let you use all three disks, however it does not give an increase in speed. It is a JBOD array; three drives in jbod would show as one drive with the sum of the capacity.

    I think for what you want, two drives in raid 0 with a third for backups would give you the best performance.
     
  6. thrillkiss

    thrillkiss Thread Starter

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    Thanks again crjdriver, I am planning to use solid state flash drives. They promises to give higher sustained rates compared to rotating drives, though it would cost me. On the otherhand, I need to have sustained R/W rate of 160MB/s. Any suggestions

    thanks in advance.

    regards :)

     
  7. crjdriver

    crjdriver Moderator

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    The only mechanical drive that comes close to that is scsi raid 0 using 15,000 rpm 8 meg cache drives. I think they are around 150 mps. A setup like that will be expensive.
     
  8. thrillkiss

    thrillkiss Thread Starter

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    I have someone ask me, hope you can help me.
    They are using dual Xeon Processor and 13GB RAM. They are planning to use 11.5GB as cache for the R/W. I was thinking of a RAID5 or RAID 7 setup with at least 12 to 24 150GB HDD. What do you think?

    thanks again :)


     
  9. crjdriver

    crjdriver Moderator

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    I have only setup raid 0, 1, and 01. I really have almost no knowledge of raid 5 or 7.
     
  10. thrillkiss

    thrillkiss Thread Starter

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    thanks buddy, i do apologize, hope i din't anoy you that much, i'm a little hype about this. Got some answers/ recommendations with microsoft developers and try to simulate those.
    it was nice chatting with you
    :)
    GODSPEED....


     
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