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Re: ag selection

To: Eric Sandeen <sandeen@xxxxxxxxxxx>, xfs@xxxxxxxxxxx
Subject: Re: ag selection
From: Bernd Schubert <bernd.schubert@xxxxxxxxxxxxxxxxxx>
Date: Mon, 11 Nov 2013 20:42:40 +0100
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Hello Eric,

On 11/11/2013 07:30 PM, Eric Sandeen wrote:
On 11/11/13, 12:23 PM, Bernd Schubert wrote:

One of my colleagues benchmarked this on one of our fast systems and another
colleague current needs this system for other tests, so I don't have the
exact parameters. However, it was for sure formated with options like these:

mkfs.xfs -d su=256k,sw=10 -l version=2,su=256k -isize=512 /dev/sdX

and mounted with these options:

mount -onoatime,nodiratime,largeio,inode64,swalloc,allocsize=131072k,nobarrier 
/dev/sdX <mountpoint>

With all due respect, this is excessive knob-twiddling.  Slow down.  ;)

* V2 logs are default already, so -l version=2 is redundant.

Well, some of our customer are using fhgfs + xfs on old systems and we don't want to create a list

"with kernel/xfsprogs version < xyz, you need knob abc..."

So better add it by default, as long as it does not hurt.

* noatime implies nodiratime, so specifying both is redundant.

Ok, I didn't add it to our default options, but I also didn't care about it.


* "largeio" only changes the st_blksize value reported (from default page size 
to, in your case, the total stripe width).  Does that actually affect your application 
behavior?

Fhgfs does not care about it, but for some backup tools (I think rsync does/did? read it) it helps.



Backing up, what kernel & what userspace versions are you testing?

xfsprogs-3.1.1-10.el6 + kernel 3.11.



Cheers,
Bernd

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