On Dienstag, 17. Januar 2012 Stan Hoeppner wrote:
> Thanks for the correction/reminder Dave. So in this case the first
> sector of the first partition would need to reside at LBA1280 in this
> array (655360 byte stripe width, 1280 sectors/stripe), as the
> partition table itself is going to occupy some sectors at the
> beginning of the first stripe. By creating the partition at LBA1280
> we make sure the first sector of the XFS filesystem is aligned with
> the first sector of the 2nd stripe.
There's one big problem with that: Many people will sooner or later
expand and existing array. If you add one drive, all your nice stripe
width alignment becomes bogus, and suddenly your performance will drop.
There's no real way out of that, but three solutions come to my mind:
- backup before expand/restore after expand with new alignment
- leave existing data, just change mount options so after expansion at
least new files are going to be aligned to the new stripe width.
- expand array by factors of two. So if you have 10 data drives, add 10
data drives. But that creates other problems (probability of single
drive failure + time to recover a single broken disk)
mit freundlichen Grüssen,
Michael Monnerie, Ing. BSc
it-management Internet Services: Protéger
http://proteger.at [gesprochen: Prot-e-schee]
Tel: +43 660 / 415 6531
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