On Wed, 15 Dec 1999, Jeff Hoffmann wrote:
> > my preference tends to be software raid...whatever I've ever seen as far
> > as hardware raid is concerned has been quite slower then software
> > raid...and this is with high-end servers...
>
> i kind of question this, and here's why: i just set up a linux dual
> P3/256MB with 4 software raid 5 volumes and even loading data into one
> of the databases slows it to a crawl. i've been looking around because
> it seems absurd that the machine should slow down so much. i haven't
> really found any answers, but i have seen several places which told me
> that software raid under linux _isn't_ safe for multiprocessors & no
> place has told me for sure that it is.
What filesystem? I know (thank god) very little about Linux, but
there have been comments here by some Linux folks (Thomas, wasn't it
you?) that indicated that ext2fs sucks for this? Are you running with
fsync() on or off?
> appreciate it. assuming this is the case, software raid wouldn't be a
> big problem if you don't do a lot of heavy writing.
Most of my RAID tests are on Solaris+Disksuite...with good drives
in the machine, my writes are something like 18MB/s to the drive, stripe'd
and mirrored...I think reads worked out to be 19MB/s...(bad drives, same
setup, same machine, same OS, were net'ng me something like 3MB/s...really
killed performance *grin*)
Marc G. Fournier ICQ#7615664 IRC Nick: Scrappy
Systems Administrator @ hub.org
primary: scrappy@hub.org secondary: scrappy@{freebsd|postgresql}.org