[OpenAFS-devel] tuning underlying filesystems for afs

Horst Birthelmer horst@riback.net
Thu, 14 Oct 2004 19:14:51 +0200

On Oct 14, 2004, at 5:50 PM, Martin MOKREJ=8A wrote:

> Hi,
>  I'm installing new afs cell and configuring huge afs server - 1TB
> raid5 array on a dual-controller based on adapter U160. It has 6 GB=20
> RAM,
> 2 xeon CPU's 3 GHz. It runs linux-2.4.28-pre3 kernel.
>  AFS has inode based and namei based fileservers. What is their=20
> difference
> in terms of performance?

There isn't any reason for installing an inode fileserver and Linux=20
fileservers are namei by default.
 =46rom now on I'm referring to namei fileservers...

>  Filesystems are usually tuned for large or small files. What is the=20=

> case of
> fileserver? The /vicepX partitons are mostly filled with few small=20
> files,
> which corresponde to volumes if I'm right. That has nothing to do with=20=

> size of
> files stored in afs volumes, I know ... but should I tune for "huge"=20=

> or "small"
> files?

It has to do with the size of your files. What hasn't is your=20
directories but the files will definitely be there but not in any=20
directory you would recognize from where it is on your AFS client.
So if you have a lot of small files ... on your fileserver will be a=20
lot of small files.
Your volumes and files get organized by the fileserver using an=20
algorithm documented based on some hashing but I think you don't want=20
to know about it ;-)

>  I expect to have several files above 1GB in afs volumes, in general=20=

> more
> huge files then small ones.
>  AFS/kernel mounts /vicepX partitions automatically? However, for=20
> example xfs offers
> several mount options, which affect performance. How can I make=20
> advantage of
> such options under afs?

AFS doesn't do anything by itself!!
Nobody will mount your partitions until you do that (on the server=20
side) and the parameters are in your hands as well. Tune as you want or=20=

need it.
The fileserver on startup will just look at directories named /vicepXX.=20=

That's all...

>  I'm attaching my current results from bonnie++ tests. In general, xfs=20=

> is fast
> equally as reiserfs, except random operations. For random operations,=20=

> reiserfs
> is the best, them comes ext2, ext3 and xfs as the last one. At least =
> I interpret the numbers correctly.

I can't and won't interpret your decisions regarding the tuning.