What RAID setup do you recommend for Microsoft EBS running on VMWare?

Posted on 2009-04-21
Last Modified: 2013-11-10
Our company has purchased a new Intel x3500 Server and we intend to run VMWare on it and install 4 virtual hosts to make up the 4 servers for Microsoft Essential Business Server. Our environment is about 100 users. The functions of these four servers will be; (domain controller + file server)(MS SQL)(Exchange)(security+firewall). The physical Intel server will come with 8 x 300GB disks and I am unsure as to what is the best way to setup the RAID of these disks.

I have read that MS SQL and Exchange should preferrably run on their own physical disks. Does this still apply in a virtual environment?

Do I just create one big RAID 5 disk on the server and then allocate the 2.1TB when I create the virtual servers? Or do I create a RAID setup that creates several RAID 1 disks so that each virtual server is running it's own physical disks.

I'm looking for recommendations!

Question by:spandexandy
    LVL 21

    Accepted Solution

    I assume you want to use VMware ESX(i) !?

    Virtual machines or not, it's recommended to have dedicated disks for the servers and if possible for the database, too. This will increase the performance of the VMs considerably.

    So in your case, with four VMs and eight HDDs I recommend to use four RAID-1 arrays so that each virtualized server has it's own array of two mirrored disks. To improve the performance it would be better if the Exchange database and the SQL database had a dedicated array, too. If you can add more disks, you should think about that. (don't know the exact specifications of the x3500 server)

    Of course, you could create one big RAID-5 array, but as far as I know the VMWare filesystem (VMFS) is limited to 2 TB. So maybe the array wouldn't been recognized by VMWare at all. Further, if only one disk goes offline for some reason, the performance of the whole array will be extremely low until the array is rebuild and in this case this would effect all four servers! I wouldn't rely on a setup like this in a company with 100 users.

    With dedicated RAID-1 arrays, the performance wouldn't drop if a drive goes offline and the rebuild process is much quicker.

    LVL 3

    Author Comment

    Thanks for your prompt reply. If you don't mind I will wait 24 hours before accepting your solution in case someone else has anything more to add or a different opinion.
    LVL 7

    Assisted Solution

    I concur with JBlond.
    You can create 4 RAID-1 Mirrors so that the VMware ESX can share its disk with one of the VM.

    The other VMs can have their individual RAID Mirrors.

    Please segregate your Virtual Machine Traffic by allocating separate NICs for Service Console and not to share a NIC for VMs and Service Console alike.
    LVL 8

    Assisted Solution

    Arr now kumarnirmal has introduced you to your next question.
    spandexandy can you please respond to the question of what ESX flavour are you using ESX? or ESXi.
    There's considerably more to take into account than just the array configuration but your question is about the array configuration.
    I don't necessarily agree with the other lads. There's a few thing to weigh into the decision
    What I'd be looking at is what my intended IO capabilities are..and therfore what are the individual spindles IO capability.
    Raid 1 will give equal read write performance but if you exceed the capabilites of any 1 or the 2 spindles your in trouble.
    Raid 5 will give poorer performance in general over a raid 1 but it may be sufficiaaent anlso because there are more spindles and you can write in larger stripes (as ESX wants) you may fine raid 5 averages your spindle load and therefore performs better. (after all load averaging is what virtualisation is all about)
    Do you see the point..
    If you have 1GB of ram on your array controller and of course it's a high end array controller then a raid 5 is the obvious choice.
    If it's a shitty array controller then raid1 mirrors (or raid 1+0) are the obvious choice.

    So for an assesment.
    Assuming you have a reasonable array controller with at least 512MB of ram, the battery backup module and 2 SAS chanels to your split back plain
    Without knowing more I would be looking at a raid 5.
    When you create your first logical partition use a large strip eg 512KB, this will waste some space on the ESX install partition but will give a persistent large stripe size over the other logical volumes  
    I'd initially create a 50- 70GB partition for ESX. If there's space spare leave it alone..If your installing ESXi and using a memory stick you don't need this partition.
    So if ESXi is the flavour complete your install on the memory stick, reboot the host server.
    Create your first disk of 1TB with a large stripe size, create the other logical volumes 1TB or what every you have decided is your ideal size.
    Boot to ESX. Now you will be able to add storage for your VMFS stores.
    My advice is keep the LUNS as they are, don't use extents to put them together.

    LVL 3

    Author Comment

    Thanks for the further points - I really appreciate it and I also understand that there is no "Correct" answer necessarily in this scenario! I am avidly reading it all and learning a lot. :)

    Here is further info:
    1.  We will be using ESX not ESXi
    2.  Our RAID controller will be ServeRAID 8k which I see has a 256MB buffer

    So, if I understand markzz correctly, because our RAID controller is "shitty" it won't be able to properly handle big throughput to a RAID 5 in our VMWare environment anyway. For this reason multiple RAID 1's is the way to go. Furthermore, if I understand JBlond correctly, separating the virtual machines to each have their own physcial RAID disks would also help performance of each virtual machine.

    LVL 3

    Author Closing Comment

    Thanks for your answers. Really appreciate the time you took to help me.
    LVL 8

    Expert Comment

    Just a final comment
    It will be much more cost effective to install a higher end raid controller than add more disk..
    ESX, good for you it's the right direction.
    If you install the better raid controller your 8 disks will give you 2.1TB useable rather than 1.2TB useable..
    Say you spend $1000 on the controller to get 2.1TB where as if you have to buy another 8 disks to gain another 1.2 TB of mirrored disk you will have to spend about $4000
    LVL 3

    Author Comment

    Thanks for the tip. :)

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