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Topic
  • 6 replies
  • Latest Post - ‏2012-11-11T17:03:54Z by chriscanto
SystemAdmin
SystemAdmin
4779 Posts

Pinned topic How do I find the best stripe size and raid size for my setup?

‏2012-10-31T11:14:22Z |
Hi,

We are about to buy a V7000 setup (2 enclosures), but before we do, I would like to know how many disks we should buy with it. To figure this out, I need to find out how many disks we will be using in each RAID-5 MDISK and also remember to calculate for the hotspare.

We will only be running VMware in this environment and VMware 5.1 VMFS works in 1MB blocks. Now, in a traditional SAN (say DS4700) I would divide 1024 with the number of data disks in the raid-5 then add the parity disk and a hotspare (which is the way to go about it for optimal performance). That means e.g. a SAN with 10 disks configured with 1 hotspare (9 disks left) and minus the parity disk in raid-5 (8 data disks left): 1024 / 8 = 128. Hense the stripe size should be configured for 128k for optimal performance.

But this is no DS4700. It's the V7000 and now there's all sorts of things to take into account: No. of disks, Disk Pools, Extend Size, etc. Plus the fact that the V7000 (to my understanding) places volumes (or LUNs) on top of several MDISKs so that the data is kind of floating across all disks in the Disk Pool (which e.g. consists of 6 MDISKs).

So my question is this:
If we have 2 enclosures and want to use as many disks as possible, but at the same time make sure that stripe size etc. match for best performance, which stripe size/configuration should we use? Or how do we calculate the best solution?

As I said we will be getting 2 enclosures and we will be using 600GB disks in RAID-5 MDISKs, to get most storage possible. So a maximum of 48 disks. But remember to calculate 1 hotspare for each of the two enclosures as well.

I hope there's a V7000 expert out there who can help us :) Let me know if further details are required. Thanks in advance.

/Rasmus
Updated on 2012-11-11T17:03:54Z at 2012-11-11T17:03:54Z by chriscanto
  • SystemAdmin
    SystemAdmin
    4779 Posts

    Re: How do I find the best stripe size and raid size for my setup?

    ‏2012-11-02T12:54:38Z  
    88 reads and not one reply? :(
  • al_from_indiana
    al_from_indiana
    28 Posts

    Re: How do I find the best stripe size and raid size for my setup?

    ‏2012-11-02T13:35:48Z  
    I'm not sure if this helps but for Windows its 64KB: http://www-01.ibm.com/support/docview.wss?uid=ssg1S1003291

    On another note, how did you come up with the equation 1024/x for calculating the segment size?
  • SystemAdmin
    SystemAdmin
    4779 Posts

    Re: How do I find the best stripe size and raid size for my setup?

    ‏2012-11-05T07:57:55Z  
    I'm not sure if this helps but for Windows its 64KB: http://www-01.ibm.com/support/docview.wss?uid=ssg1S1003291

    On another note, how did you come up with the equation 1024/x for calculating the segment size?
    Thanks for your answer, but I'm afraid it's not what I'm looking for.

    The equation is among other places from:
    https://www.ibm.com/developerworks/mydeveloperworks/blogs/storagevirtualization/entry/configuring_ibm_storwize_v7000_and_svc_for_optimal_performance_part_121?lang=en

    /Rasmus
  • SystemAdmin
    SystemAdmin
    4779 Posts

    Re: How do I find the best stripe size and raid size for my setup?

    ‏2012-11-08T08:49:07Z  
    I'm supprised noone has an answer to this. What do you V7000 owners do in general - just use the default settings and don't bother about stripe size etc.?
  • djole_k
    djole_k
    41 Posts

    Re: How do I find the best stripe size and raid size for my setup?

    ‏2012-11-08T10:30:19Z  
    Hi, the answer is: It depends!

    Lets have a look to the architecture of a V7000. Instead of builing single Arrays with defined Block/Stripe-sizes the V7000 has this interal structure:

    On array of disks (for example RAID5 8+P) is defining exactly on LUN (mdisk = managed disk) and normaly you put several mdisks into a storage pool (or mdisk group). And then you create a Volume (or vdisk) for a host which is hopefully "striped" (thats the default setting). On a DS3xxx you build single arrays and put the volumes directly on it. and then you have to define block and stripe sizees. The - let call it - Segment size (extent size) on V7000 is at least 16 MB and it does not define a stripe size on the array, is a parameter for the storage pool.
    The default ist normaly 256 MB and that's the part of the volume which will be striped over all mdisks within a storage pool.

    An example: the storage pool contains 4 mdisks, the volume has 1 GB and the extent size is 256 MB. The vdisks has 4 extents, one on each mdisk. Each mdisk has contains 8 data-disks. And each physical HDD has a segment of 32 MB of the Volume.

    There's also "grains" with a size of 64 KB and 256 KB. But this grains are only used for FlashCopy an Thin Provisioning.

    At the end, this discussion looks very similar to AIX LVM Striping or Poorman (or PP) Striping. I think you will find lots of interessting discussion about it. The question is the same: Striping in KB blocksizes or in large MB-Segments.

    And the winner is...

    What do you think?
  • chriscanto
    chriscanto
    280 Posts

    Re: How do I find the best stripe size and raid size for my setup?

    ‏2012-11-11T17:03:54Z  
    You could try asking Barry:

    https://www.ibm.com/developerworks/mydeveloperworks/blogs/storagevirtualization/entry/open_forum_q_a_58?lang=en