Best RAID setup
Hello, I was wondering what would be the best RAID configuration for me, we have recently purchased an extra hard drive and am just wondering if this would be an opportunity to change my config. The RAID is using hardware level RAID. My setup is as follows with 5 Disks 2 are in RAID 1 and host the OS 3 are in RAID 5 and host VHD’s This is a Hyper-V server, there is also one VHD on the RAID 1 due to using space efficiently. I have always been under the impression this is generally the best way to configure it, but now we have bought another hard drive this brings me up to 6 disks and I am wondering if I should: Leave it as RAID 1 and RAID 5 Or, convert the entire lot to RAID 5. What are your suggestions and why would you pick either one? Steve
February 11th, 2011 1:42pm

Are all the drives the same size and speed? In general, while its desirable to keep I/Os for OS vs applications segragated, there is alot of wasted space and wasted thoughput in that configuration. Over all in this small implementation its pick your poison. Space wise and overall, a single RAID 5 will probably get you the best overall performance for the system as a whole. This is because you will have more spindles and throughput for all I/O operations. Spindles tend to trump everyting. The theory works like this, each disk/spindle gives you say an estimated 300MB/s throughput * 6 drives = 1800MB/s throughput. If you break that down to 2 and 4 drive RAID configurations, then you are at 600MB/s for the OS, and 1200MB/s for the data. But does your OS need 600MB/s? Or does your data need more? I subscribe to the best average performance for all theory, which puts all disks into a single group and share the I/O amongst everything, its easy to grow this scenaio when performance slows down, add more disks. The down size to this is if you are undersized your disk/spindles to start with, your OS may feel sluggish and be very noticable, but that just indicates you planned badly to begin with, and/or you need to add more spindles. What most people try is to maximize performance for single items, and this become tedious and ultimately time consuming. This is the typical maximize performance theory / implementation or design. Of course only performance testing your configuration will tell you want works for you.
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February 11th, 2011 2:32pm

Hi, If you have 6 disks, you may consider using RAID 10. By the way, the following posts discussed a similar issue, you can refer to: HDD Configuration: SAS, RAID, VHD in Hyper V http://social.technet.microsoft.com/Forums/en-US/winserverhyperv/thread/8c09b4b3-c701-4d29-ae20-f030d4a62436 RAID Configuration For Best Hyper-V Performance + Reliability http://social.technet.microsoft.com/Forums/en-US/winserverhyperv/thread/b228cf8c-4ed2-47d0-95e2-ca0018f323e4 16 SAS disk host machine and best senario for VHD's http://social.technet.microsoft.com/Forums/en-US/winserverhyperv/thread/6f6d8959-79bd-42b9-9ae2-8f73010dcf89 In addition, some guys prefer to use RAID 1 for the Hyper-V host operating system, however, some of them store some VMs in the RAID 1 due to the “space efficiently”, this will works properly, but it’s not recommend as best practice. Best Regards, Vincent Hu
February 11th, 2011 11:03pm

thank you both for your contributions, your information and references were most interesting to read. cheers. Steve
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March 19th, 2011 9:25pm

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