Very inconsistent (read) speed on UFS2

[Lev Serebryakov]

Hello, Freebsd-fs.

  Now, when I "defragmented" my large FS, I see very inconsistent read
speeds on same files. Is it Ok?

  My setup is:

 (1) FreeBSD 8.2-STABLE/x64
 (2) E4400 CPU, 2GiB RAM
 (3) 5xHDDs in RAID5 (software), controller is ICH9R.
 (4) UFS2 with 32KiB block, vfs.read_max=32 (1MiB read-ahead).
 (5) System and swap on another (6th) HDD, but swap is unused.
 (6) No periodic or background processes access FS in question at all.

 Simple program reads each of 12 files (420MiB each) 15 times in cycle
 like 01, 02, ..., 12, 01,... so, cache in memory should be thrashed, as programe
 returns to dame data every ~5.5GiB and here are only 2GiB physical
 memory in system.

-- 
// Black Lion AKA Lev Serebryakov <lev at FreeBSD.org>