Re: Stripe alignment with RAID volumes

[Dave Lloyd <dlloyd@exegy.com>]

David Chinner wrote:

 >
 > Device mapper is your friend - you can offset the start of the volume
 > on each device you use.
 >
 > We've done this in the past to allow multiple volume managers to coexist
 > on the same luns. e.g. first volume manager exists in 0-4MiB of each
 > lun, so we tell dm that each device starts at offset 4MiB rather than
 > at 0....

Device Mapper?  I haven't heard about this.

 >> Would it be possible to add a stripe start offset to XFS?
 >
 > Maybe, but I can't see how it would be a simple thing to do because
 > it would require on-disk format changes...
 >
 > Anyway, if you were configuring an XFS filesystem to do this, you
 > still need to understand the underlying geometry to get it right.
 > You may as well get your volume manager configuration correct, and
 > then we don't have to worry about it in XFS.

The latest parted will let you use bytes to size the partitions.  Stripe
aligning the begining and the end of the partition does give better
performance.

-- 
Dave Lloyd
Test Engineer, Exegy, Inc.
314.450.5342
dlloyd@exegy.com