Tuning ext3 for a FC SAN?

[Darrell Michaud]

With that much performance difference, it's unlikely the filesystem is
responsible.

You might try making a single LUN available with one of the disks (not the
96 disk RAID) as a reference point and run raw bandwidth tests again. HBA
Drivers, switch configuration, and fiber cables are normally things to
look at. The fiber cables themselves are notoriously picky about being
having perfectly clean connection points.



Kenny Lussier wrote:
> Hi All,
>
> I am not a filesystem/performance expert by any means, so I am hoping
> that I can pick up some tips and pointers here. We are currently
> evaluating a SAN, and the performance is less then stellar. We have
> simulated our production environment, which is:
>
> RHEL 4 (x86_64) u7 running the 2.6.9-67.ELsmp kernel
> Dual quad-core Xeon 3.16GHz CPUs
> 16GB of RAM.
> 15K SAS internal drives RAID1
> Two single port FC QLogic HBA's (4G/s model)
> Two Brocade FC SAN switches
> SAN from <un-named vendor>  with 96 400GB 10K drives
>
> The problem that we are seeing is that the descrepancy in I/O
> performance between local disk and the SAN throughput seems way too
> high. Using IOZone, we are getting 80MB/sec throughput for rewrites of
> 16-32MB files, with a 4K block size on the local disks. When running
> the exact same tests against the SAN, we are seeing 14MB/sec
> throughput. I expect to see a difference between local and remote
> storage, but that seems to be outside the realm of normalcy.
>
> So, my question is, is there something that I need to do to tune the
> ext3 filesystem? Are there options that I should use when I create the
> file system to optimize it, or mount options that should be in fstab
> to increase performance? Are there any pointers anyone may have for
> optimizing a system for use as a database server connected to a FC
> SAN?
>
> TIA,
> Kenny
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