How to Disable RAID Feature on HP Smart Array P400

Too many imponderables. For example, how are the disks set up? If the logs and data share the same disks the random I/O from the data areas will disrupt the log traffic, which is mostly sequential I/O and is disproportionately affected by a busy random access workload on the same disks.

Without some more insight into your configuration I can't really say what might be causing the problem.

For example, 60MB/sec off a RAID is about right for a 4-disk RAID-5 or RAID-10 with 64k stripes and 15k drives. Each drive will read one 64k stripe per revolution of the disk (about 250/sec for a 15k drive) which gives you 15MB/sec per drive.

The average seek time for a 15k disk is around 3ms across the whole disk. On a mostly contiguous 10GB file on a RAID volume with (say) 146GB or 300GB disks and a bit of help from the cache I could see 30MB/sec being a reasonable figure for a disk array configured as described above. It would indicate averaging a data read about every two revolutions of the disks.

That's a thought off the top of my head for a configuration one might reasonably expect to see on an ML350. However, I have no idea if that matches your actual configuration, so I can't really comment on whether the observations are relevant in your case.

This is several questions in one, so I'll try to address a few of them.

I typically set Smart Array controllers to leverage a higher write cache ratio. I prefer to have 75% write cache because the OS (using the XFS filesystem) caches aggressively. XFS will make a difference, but what are you tuning for? Are you tuning to simply achieve specific numbers, or is there an application requirement driving this?

ext3 isn't the fastest filesystem out there. But you have some mount options (e.g. noatime) and journal settings you could tweak.
I don't use LVM, especially with HP controllers that can provide many of the same benefits.
You have I/O scheduler and elevator settings (e.g. noop or deadline, in this case) that can be tuned, but that's a function of your application's actual needs.

If you do go with XFS, try a basic config then try some advanced configuration settings. Over time, I've ended up with mount parameters very similar to the one in the original link.

I just ran the following iozone command line on an XFS partition contained within a DL380 G5 with P400i, 12GB RAM and 8 x 146GB 10k drives. The elevator is set to deadline:

Command line used: iozone -t1 -i0 -i1 -i2 -r1m -s24g

initial writers  =  348957.75 KB/sec
rewriters        =  335130.03 KB/sec
readers          =  132851.70 KB/sec
re-readers       =  137116.27 KB/sec
random readers   =   35774.41 KB/sec
random writers   =  250618.38 KB/sec