xfs help question

xfs help question

[Marko Weber|8000]

hello again me ;-),
i thought best place to ask this is here.
i read the faq alot last days but have still questions:

i got a server now with 4 Disks,
i plan to do an raid5 with linux soft raid.
On the server is planed to store 'larger' from 1GB up to 60GB.

what would be best settings when formatting with xfs?
is it better to use '-b size=4096' or the '512'?
should i manipulate the '-i size=' to 2048? or use the default?

i also dont get it with the write-disk cache at all,
its an linux softraid, is the best then to use 'nobarrier' and let the
'disk write cache on'?

or is best solution on linux softraid 'disk write cache' on with xfs 
barrier on?

also, should i tweak with sunit,swidth? and how do i calculate best 
setting?

thanks for any tipps n hints

marko

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Re: xfs help question

[Emmanuel Florac]

Le Sun, 30 Mar 2014 09:12:20 +0200 vous écriviez:

> i also dont get it with the write-disk cache at all,
> its an linux softraid, is the best then to use 'nobarrier' and let the
> 'disk write cache on'?
> 
> or is best solution on linux softraid 'disk write cache' on with xfs 
> barrier on?

It depends. write cache without an UPS is a very efficient way to lose
data. However  if you only care about performance, let write cache on
and barriers off.

> also, should i tweak with sunit,swidth? and how do i calculate best 
> setting?

With a recent kernel, mkfs.xfs should determine automatically the md
geometry, so no, don't try to tweak su and sw.

-- 
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Emmanuel Florac     |   Direction technique
                    |   Intellique
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Re: xfs help question

[Dave Chinner]

On Sun, Mar 30, 2014 at 09:12:20AM +0200, Marko Weber|8000 wrote:
> 
> hello again me ;-),
> i thought best place to ask this is here.
> i read the faq alot last days but have still questions:
> 
> i got a server now with 4 Disks,
> i plan to do an raid5 with linux soft raid.
> On the server is planed to store 'larger' from 1GB up to 60GB.
> 
> what would be best settings when formatting with xfs?
> is it better to use '-b size=4096' or the '512'?
> should i manipulate the '-i size=' to 2048? or use the default?

Use the defaults.  The defaults on md/dm raid will do the right
things to configure the filesystem and handle crash safety properly.

Unless you have experience with XFS and the storage stack and know
exactly what you *need to do*, tweaking knobs will only cause bad
things to happen to you and your data.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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