UFS2 with Soft Updates Robust?
conover at rahul.net
Wed Dec 22 22:37:29 PST 2004
Damien Hull writes:
> On Tue, 2004-12-21 at 21:31 -0500, Chuck Swiger wrote:
> > John Conover wrote:
> > > Is UFS2 with soft updates the most robust file system in freebsd?
> > No, although UFS2 with softupdates is robust enough for production use.
> > If you make the filesystem writes syncronous and disable write caching on the
> > hard drive, you will improve the robustness at significant cost to performance.
> Are you saying that the UFS2 file system sucks? If so what options does
> one have?
> I've read that softupdates should be turned on. How much of a
> performance loss will I see if I turn softupates off?
Oh, no, not at all, Damien-I consider UFS/FFS quite sturdy. I put it
in a PC with softupdates on, (and no other options, like cache write
through, synchronous writes, etc.,) and for 30 minutes cycled the
machine's power switch 15 times, hitting the power as soon as fsck
started, etc. to see if I could induce an exception/fault scenario
with something it couldn't fix auto'magically. Also, I hit the power
switch with a dozen cat /dev/zero > bigfile1, ..., processes,
too-after they had filled up about 20G of spinning real estate.
UFS/FFS withstood the abuse well.
So I have been told, for maximum reliability/durability, cache write
through should be enabled, along with synchronous writes-albeit at a
substantial speed penalty, (I don't know how much-that's a test for
So far, I've done this on about a half dozen open source OS
distributions, and one Sys V Rel. 4 with Veritas journaling FS.
FreeBSD and Veritas are the only two that survived.
For the record, the box is an Intel reference MB, and an Adaptec
2940UW, with a Fujitsu 35G SCSI drive. All out of the box default
settings. No RAID.
John Conover, conover at rahul.net, http://www.johncon.com/
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