Re: Verify filesystem is aligned to stripes

Michael Monnerie
2010-11-26T14:04:19Z

[-- Attachment #1.1: Type: Text/Plain, Size: 1335 bytes --]

On Freitag, 26. November 2010 Dave Chinner wrote:
> FWIW, for workloads that do random, small IO, XFS works best when you
> turn off aligned allocation and just let it spray the IO at the
> disks. This works best if you are using RAID 0/1/10. All the numbers
> I've been posting are with aligned allocation turned off (i.e. no
> sunit/swidth set).

That's interesting to read.

Why would sunit/swidth be slower then? I'd thought that XFS then would
know one stripe is 64k and I have 8 disks so it should try to pack
8*64=512kb in one junk on disk, and that especially for small files it
would write them like that.

The man page just says inodes, log are stripe aligned, and file tails
>512k extended to full stripes on append. I thought that even the
inode/log alignment alone would help a lot.

Now what is the advantage on skipping sunit/swidth altogether?
And what is the difference when it's on RAID10 to RAID6?

I'm always eager to understand performance issues ;-)

--
mit freundlichen Grüssen,
Michael Monnerie, Ing. BSc

it-management Internet Services: Protéger
http://proteger.at [gesprochen: Prot-e-schee]
Tel: +43 660 / 415 6531

// ****** Radiointerview zum Thema Spam ******
// http://www.it-podcast.at/archiv.html#podcast-100716
//
// Haus zu verkaufen: http://zmi.at/langegg/

[-- Attachment #1.2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 198 bytes --]

[-- Attachment #2: Type: text/plain, Size: 121 bytes --]