Performance Differences Between RAID 0, 1, 5, 6, 10 – How to Compare

Buy a copy of "postgresql high performance" by Greg Smith. It is a great Book and two or more chapters are about Disk Hardware and filesystems. You will learn a lot.

In short: there is no short answer.

But i will try to summerize:

• don't use ext2 until you know what you are doing.
• with ext3 beware of checkpoint spikes because of fsync calls, see page 113 and 82 and 79
• use ext4 or xfs
• there are other options

But as you are really asking yourself what FS to use, you should read the book!

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.