Tag Archive for 'ufs'

FreeBSD: vfs.read_max for Hardware RAID

Tested with: bonnie -s 2048, FreeBSD 7.0 UFS2 , Hardware RAID 5 (6 PATA 7200rpm 250G disks)
vfs.read_max=8 (default)

-------Sequential Output--------
-Per Char- --Block--- -Rewrite--
Machine MB K/sec %CPU K/sec %CPU K/sec %CPU
2048 25812 24.8 26483 6.6 13886 4.4
---Sequential Input-- --Random--
-Per Char- --Block--- --Seeks---
K/sec %CPU K/sec %CPU /sec %CPU
32162 32.5 33386 5.1 232.3 1.5

vfs.read_mas=128

-------Sequential Output--------
-Per Char- --Block--- -Rewrite--
Machine MB K/sec %CPU K/sec %CPU K/sec %CPU
2048 25380 24.3 25949 6.5 13956 4.3
---Sequential Input-- --Random--
-Per Char- --Block--- --Seeks---
K/sec %CPU K/sec %CPU /sec %CPU
41060 43.4 42839 8.3 224.9 1.4

vfs.read_max=256

-------Sequential Output--------
-Per Char- --Block--- -Rewrite--
Machine MB K/sec %CPU K/sec %CPU K/sec %CPU
2048 25714 24.3 25939 6.5 13966 4.3
---Sequential Input-- --Random--
-Per Char- --Block--- --Seeks---
K/sec %CPU K/sec %CPU /sec %CPU
41442 43.8 43737 8.6 225.2 1.5

Conclusion: No performance gain on random access, but about 25% better sequential read performance.

FreeBSD gjournal and UFS snapshot

Recently I am testing a new feature in FreeBSD 7.0: gjournal. However, taking a snapshot on a journalized ufs causes kernel panic. (Size of the RAID is 5TB)

panic

And I cannot write into the filesystem when I am taking a snapshot, and ever can not read data from it. We should use ZFS or NetApp when we need filesystem snapshot in FreeBSD…