Re: Two hour parity check

[Gary <vex555@gmx.net>]

On Mon, 2 Feb 2004 09:57:43 -0800
Scott Francis <darkuncle@darkuncle.net> wrote:

> be glad it's only 2 hours. :) I set up a RAID5 of 4x160GB 5400RPM IDE
> disks a while back (2 disks per promise PCI IDE card), and parity
> rebuild on that takes _fourteen_ hours. Not fun. However ...

wow - thats totally useless for a web/mail server. Even two hours every
couple of months is going to have clients bitching.

> It's possible to have this run in background and continue normal
> bootup, and even use the system in the meantime (obviously you can't
> use the RAID filesystem until parity is rebuilt, but the rest of the
> system is useable).

Umm, well all the essential stuff is on the raidset - so that doesn't
help much :)

> definitely you want multiple filesystems. At the minimum, / /tmp /var
> /home/usr and /usr/local.

Done this ecxept for the /usr/local. Why that one? Also I realise that
mail/web docs/ logs etc go in /var so that has to be the biggest, but
how big do /usr /usr/local /home and /tmp need to be ? (P3 1.2gig 1gig
ram, 2 gig swap)
 
> fsck will run on every filesystem not cleanly unmounted. However, that
> probably won't be any slower than a single massive partition (and you
> may find that it will be faster). You may also wish to use the soft
> updates mount option on your RAID filesystem; I did that (450GB
> filesystem) and read/write performance improved considerably.

I've heard of problems with softupdates. I want reliability and uptime
over performance.

> cheap IDE solution. I avoid the parity rebuild problem by being _very_
> careful to cleanly unmount the filesystem and the RAID set.

The box will be in a co-lo location 4 hours drive from here with ups and
diesel backup so it should be OK - but who knows?

regards
Gary