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raid1 15k rpm or raid5 10k rpm for iSCSI

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  • raid1 15k rpm or raid5 10k rpm for iSCSI

    Hello,
    I need to choose from 2 servers for iSCSI storage (reading activity):

    1. 2 - 146GB 15K

    2. 3 - 72GB 10K

    Could raid 1 with faster disks be better than slower disks in RAID 5?

    Thanks,
    Michael.
    "When you hit a wrong note it's the next note that makes it good or bad". Miles Davis

  • #2
    Re: raid1 15k rpm or raid5 10k rpm for iSCSI

    Yes
    RAID 1 can be faster for reading (compared with RAID 5) as a good controller will read both drives at once
    ALso there is the performance improvement of the faster drives
    Tom Jones
    MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
    PhD, MSc, FIAP, MIITT
    IT Trainer / Consultant
    Ossian Ltd
    Scotland

    ** Remember to give credit where credit is due and leave reputation points where appropriate **

    Comment


    • #3
      Re: raid1 15k rpm or raid5 10k rpm for iSCSI

      Ossian,
      my feeling is equal to your answer.
      But, as we know raid 5 advantage is reading performance when there is no reading advantage of raid 1. I guess 15K could make the trick.

      This what I found on the other forum:

      "Since you're going to create RAID for read activity, take maximum theoretical performance.
      10k ~ 140-160 IOPS which leads to 420-480 IOPS on 2+1 RAID 5
      15k ~ 180-200 IOPS which leads to 360-400 IOPS on 1+1 RAID 1"

      The contradiction between your answer and the above leads to confusion
      Could you elaborate...

      Regards.
      Michael.
      "When you hit a wrong note it's the next note that makes it good or bad". Miles Davis

      Comment


      • #4
        Re: raid1 15k rpm or raid5 10k rpm for iSCSI

        A link to the "other forum" would be good!

        From MS courses, RAID 1 came out faster than R5 in reading as the same data is on both drives, wheras R5 has different data on each drive in the array -- I'm sure would give you more info

        Also, R1 is definitely faster in writing (despite writing to 2 drives) as there is no parity calculation
        Last edited by Ossian; 7th April 2010, 09:22.
        Tom Jones
        MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
        PhD, MSc, FIAP, MIITT
        IT Trainer / Consultant
        Ossian Ltd
        Scotland

        ** Remember to give credit where credit is due and leave reputation points where appropriate **

        Comment


        • #5
          Re: raid1 15k rpm or raid5 10k rpm for iSCSI

          Originally posted by mla View Post
          Hello,
          I need to choose from 2 servers for iSCSI storage (reading activity):

          1. 2 - 146GB 15K

          2. 3 - 72GB 10K

          Could raid 1 with faster disks be better than slower disks in RAID 5?

          Thanks,
          Michael.
          Michael,

          Do you have access to both of the servers? If so you could use a tool like IOMeter to run some quick tests to gather actual numbers.

          -Jason
          MCSA/MCSE 2K3,MCITP:ESA,MCTS x 4,VCP x 2

          Comment


          • #6
            Re: raid1 15k rpm or raid5 10k rpm for iSCSI

            Jason,
            I don't have access to both at the same time.
            I took dl360 g4 with 2 146GB 15k to our work lab.
            Thanks for the tip about IO tool.
            Sure the best way is to test both. But we often rely on theory.
            We just testing some things so wanted to choose the best iSCSI server from 2 available. If I will have time probably I will bring the second one with 3HDs RAID 5.

            Thanks,
            Michael.
            "When you hit a wrong note it's the next note that makes it good or bad". Miles Davis

            Comment


            • #7
              Re: raid1 15k rpm or raid5 10k rpm for iSCSI

              raid-5 performance is heavily depending on the amount of spindles you use. Typically, less than 4 spindles, the performance is not great, ad over 10 it also starts to slow down. In between though, especially around 7-8 spindles, you'll get a better performance than with raid1.
              Real stupidity always beats Artificial Intelligence (c) Terry Pratchett

              BA (BM), RHCE, MCSE, DCSE, Linux+, Network+

              Comment


              • #8
                Re: raid1 15k rpm or raid5 10k rpm for iSCSI

                and one more thing - since you're talking about iSCSI, I'm pretty certain the network side of things is going to be the bottleneck, even with multipathing.
                Real stupidity always beats Artificial Intelligence (c) Terry Pratchett

                BA (BM), RHCE, MCSE, DCSE, Linux+, Network+

                Comment

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