Reiserfs vs XFS .. Now : How to improve IO disk speed.

Johan De Meersman jdm at operamail.com
Wed Apr 12 02:38:08 CDT 2006


Jean-Francois Bouchard wrote:

>To give more info : we got 14 disk of 300 GB 10K , RAID 5 config. That 
>is linked with 2 U320 to our file server.
>  
>
Changing out the disks for 15Ks would help, as would replacing them by
smaller ones - but the latter obviously requires rebuilding the raid
array because you're going to run out of space.

>We use the array as a DB server, I mean, a lots of little file that 
>contain what should be in a real DB .. Yes I know , we should use a real 
>DB system .. But when you got everything setup .. You don't want to 
>change things.
>  
>
ReiserFS, being an object-based filesystem, has a number of similarities
to a DB :-)

>We have 2 idea to speedup things :
>
>1- Buy a solid state HD and put the XFS journal on it.
>  
>
I think you can safely spare yourself the expense of solid-state there.
The journal is used for writes only, and in a mostly sequential fashion.
Sticking it on a separate disk is a good idea, though, but make sure you
stick it on a raid-1 lun :-) Solid-state would be very good for your
data disks, as they're filled with small files, so there's going to be a
lot of random access.

>2- Do an other File server that will split the load .. (Also more ram 
>for cache)
>  
>
obviously, but I think it's a reasonable assumption that you'll need to
change the application to be awares of this, so you can use the
opportunity to implement the filename hashing I mentioned previously as
well - no (affordable) hardware solution is going to provide you with
the speed-up that that will give you.

>>I agree that filesystem choice may not help much. Don't think there's much
>>to index in a flat directory.
>>    
>>
You'd be surprised how different filesystems can behave when faced with
large numbers of small files.



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