[SunHELP] Journaled Filesystems (thanks to sunhelp.org)

[Katherine Strojny]

> Thats a really neato feature.....how come SUN does not have logging turned
> on by default.
>
> IS THERE A DOWN SIDE TO LOGGING??

Check out this archive:
http://www.sunmanagers.org/pipermail/summaries/2002-January/002177.html

I don't how well this translates across platforms and file system types, but
my experience on HP-UX was that logging significantly increased run time for
highly disk-intensive operations.  In our benchmarks, we were able to
realize a 30% run time improvement by setting an application to use a temp
file on an unlogged, traditional Unix file system (hfs) instead of on
logged, unstriped vxfs.  In contrast, we tried a few runs with striping the
logged vxfs over multiple controllers, and that only got us about 5%
improvement.  This was for translation of a large EDI file using RMS
OmniTrans on HP-UX 10.20.  Disk I/O had been identified as the bottleneck
due to the way that particular version of OmniTrans was using disk-based
temporary storage--should have been in memory, and they fixed that in a
later release.

OTOH, back to Solaris, this article says you can actually improve
performance by using UFS logging, at least for the particular test the
author used:
http://www.itworld.com/Comp/2377/swol-0922-supersys/pfindex.html
(Kind of cool, I wouldn't have guessed--but it probably goes without saying
that you'd want to do your own realistic benchmarking if performance is a
concern.)

-k