[rescue] Weird I/O behavior

[David Passmore]

On Mon, Jan 28, 2002 at 02:38:47PM -0000, Chris Byrne wrote:

> I'm seeing something strange here. I'm doing some I/O throughput testing on
> large file transfers from local storage to a SAN.
> 
> The SunFire is seeing sustained writes of between 15 and 18MB/sec with peaks
> of around 20 and dips into the 10-12 range. This is what we would expect.

What kind of disk(s) are you transfering the files from? A single root disk?
If so, I don't see how you're able to get 15-20MB/sec throughput back and
forth.

> Read performance for all of the systems is identical with sustained reads
> around 20MB/sec with peaks of just under 30 and troughs of around 15
> 
> All are going to the same filesystem (not at the same time of course), a
> 14x72 gig 0+1 store, broken into several testing LUNs running VxFS and
> volume manager with default install parameters and no optimisations. Similar
> though slightly faster result occur for a raid 5 store. All raid is done in
> the array none in software.

What kind of array is it? Are you deporting the VxVM disk groups on one
machine, then importing them on another for testing? Does the array have
write cache, and if so, how much? Try disabling DMP on both platforms to see
what happens.

David