Best RAID for the virtualized servers

Posted on 2011-04-19
Last Modified: 2012-05-11
Hello experts!

I havent find this question, only partially so here it goes.
I´ve seen experts saying that the best RAID for an ESXi server would be RAID 10 or RAID 5.
In the other side, a File Server would be good using RAID 1 for OS and RAID 5 for data.
But what would be a good RAID for an ESXi Server virtualizing AD and File Server?
Would it still be 10 or 5? We have like 20 lan users and 30 branch office users.

Thanks very much and sorry for the bad english,
Question by:ExileD-GoD
    LVL 116

    Accepted Solution

    When creating a RAID array for ESX, where the datastore will contain all the Virtual Machines, you want the datastore response for the Virtual Machine to be as fast as possible for read and writes.

    The best performing RAID technology for a datastore for ESX is RAID 10, and then RAID 5.

    All Virtual Machines will use the same datastore, and all virtual machines will benefit from a fast datastore using the same RAID technology.
    LVL 15

    Assisted Solution

    Personally I would recommend RAID 10. With RAID 10 you need 4 Hard Drives and should 2 of the Hard Drives fail your system will still remain operational. Also, because RAID 10 is Mirroring with Striping it performs better that RAID 5.

    With RAID 5 the parity is spread across 3 of the Hard Drives and this is why the performance is decreased. Also, you can only afford to loose 1 Hard Drive, unless you go with RAID 6.
    LVL 116

    Expert Comment

    by:Andrew Hancock (VMware vExpert / EE MVE)
    So, if you have the budget RAID 10, but it's a compromise between performance and capcacity (and cost of storage).

    RAID 10 will be good for all your virtual machines using File Servers, Active Directory Servers and SQL servers etc

    Also make sure, you select a good high performance storage controller, e.g. HP Smart Array, fast SAS/SCSI disks 10,000 rpm or 15,000 rpm. (and if selecting a HP Smart Array controller ensure you also purchase the Battery Backup Write Cache Module (BBWC).

    All these factors (RAID type, disk type SATA or SAS, disk rotational speed, Array Cache, Array Cache settings) affect the performance of the ESXi datastore, and the virtual machine performance, which is stored on the datastore.

    Virtual Machine performance is dictated by the performance of the datastore.
    LVL 12

    Assisted Solution

    I think that the best storage solution for an ESXi/ESX server or vSphere should be a SAN hardware, like an HP MSA StorageWorks, Model can be many, you have to evaluate benefit/cost relashionship, and for a Raid Configuration.

    It is way too early to think about tuning.  If you want a good bang-for-the-buck, I would start by doing a RAID1 for the most transactional data, like index files, journaling, and then go with a 3-disk RAID5.  Then you can monitor I/O metrics like queue depth and read vs write traffic and go from there.  Build the machine and give it the biggest, most I/O intensive app online first, and ask the users to write some load testing procedures on a snapshot of your data.
    LVL 116

    Expert Comment

    by:Andrew Hancock (VMware vExpert / EE MVE)
    One other factor which affects performance, is the number of disks (spinny disks or spindles) in the array, the more disks or spindles the better.
    LVL 46

    Expert Comment

    Best RAID?   A little subjective here, but here are some absolutes to narrow things down

    To append hanccoka I'd add
      * Make sure the controller is on the HCL
      * Enterprise class disks a must, not consumer class
      * Nothing wrong with mixing & matching.  Example, if you need a lot of data, but performance, then traditionally you would go with SAS / Fibre channel over SATA, typically RAID10   But you could also do a RAID5 with SATA disks, and a RAID1 with SSDs.  The former might give you 200 I/Os per second, no matter what the volume, but the latter might give you 10,000 random I/Os per second on the smaller RAID1, and 50 random I/Os per second on the RAID5 and cost less.

    Which is better?   It depends.   I always advise buying absolute minimum today, as one thing you can guarantee is that I/O will get faster & cheaper tomorrow.     Also buy the faster disk controllers, i.e. SAS-2, which is dual-pathed, and 6Gbit/sec.   You might need that today, but will be glad to have it in the future.
    LVL 46

    Expert Comment

    (So in above case, use the RAID1 for as much I/O intensive duty you can think of, index files, scratch table space, the more random and more write intensive the better.  For a few hundred bucks you can get a SSD that is capable of doing 50,000 4KB random I/Os per second.

    It would take HUNDREDS of SATA disks to do that.


    Expert Comment

    RAID 10 is definitely the best option if performance is critical. Given that you have so few users then RAID5 may be sufficient as there's likely to be less contention. I would err on the side of caution though and start with RAID 10. You can always buy more disk but it's extremely difficult to change from one raid type to the other if you get it wrong first off.

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