[CentOS] XFS on a 25 TB device

Boris Epstein borepstein at gmail.com
Wed Sep 29 13:03:03 EDT 2010


On Wed, Sep 29, 2010 at 12:58 PM, Peter Kjellstrom <cap at nsc.liu.se> wrote:
> On Wednesday 29 September 2010, Boris Epstein wrote:
>> On Wed, Sep 29, 2010 at 11:53 AM, James A. Peltier <jpeltier at sfu.ca> wrote:
>> > | However, given the size of the device I assume that this is a raid of
>> > | some
>> > | sort. You'll want to make sure to run mkfs.xfs with the proper stripe
>> > | parameters to get the alignment right. Also, you may want to make sure
>> > | your
>> > | LVM or partition table is properly aligned.
> ...
>> I am wondering if I need to worry about stripe and width though as
>> mine resides on a logical volume residing on a hardware-controlled
>> RAID 6 device (i.e., one slice as far as the OS is concerned).
>
> That is why you need to consider it. If the device is aligned on stripe size
> (chunk size * (number of drives - 2 for raid6 parity)) and the filesystem is
> made aware it can put stuff (files, metadata, etc.) so that a minimum of
> stripes are touched (less I/O done).
>
> /Peter
>
>> Boris.
>
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>

Well, you are interfering with the hardware RAID controller which
copies around and stripes data as it sees fit. I am not sure with this
many levels of abstraction I can gain any measurable performance
improvement by adjusting the XFS to the controller's hypothetical
behaviour.

Boris.


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