Re: LVM root?
On Wed, Oct 11, 2006 at 05:20:58PM -0400, dtutty@porchlight.ca wrote:
> I am lucky in that my backup-set size is small; Its been tight on a 100
> MB Zip disk and absolutley essential stuff (stuff I need to be able to
> access absolultly from anywhere, any time) fits on one floppy in gzipped
> plain-text. My approach for the new root drive was to buy the most
> reliable drive I could. If it dies, get a new drive and reinstall,
> restore from backup and carry on.
>
> Your approach using Raid may be overkill for me, I don't know.
>
> The board itself has hardware SATA raid available. If I go for raid,
> then I'll ask here for the advantages/disadvantages.
Unless you have a high end server board, you do not have onboard
hardware raid. You have onboard fake raid (which is software raid done
in the bios and the windows driver). Linux's software raid is faster,
and more portable than fake raid, and fake raids don't have particularly
good support in linux yet. The only time they make sense to use is on
dual boot systems where you want to use the fake raid for windows, in
which case having linux able to use it to can make life simpler.
> More to the point for me, though, is where can I get current howtos or
> guides on fixing problems when things are in raid or LVM? Its a whole
> new world for me and the LDP HOWTOs are too out of date, and
> debian-reference doesn't cover it.
The installer supports setting it all up. It isn't very hard. Create
two partitions on each disk (identical layout for each disk), set both
partitions to be used for software raid, then select the software raid
menu on the partition menu, create a raid1 on each pair of matching
partitions, then return to the partition menu and set the use type of
the large second raid to be used as a physical volume for lvm, go to the
lvm menu and setup your lvm's for swap, home, usr, and so on, then
return and set the use type of the first raid to / (root) (I recommend
ext3), and set the mount point and filesystem for each of the lvm's and
also set the swap lvm to be used for swap. Then exit the partitioner
and complete the install.
> At this point I'm leaning to the single disk, regular / at 512 MB (/tmp
> is separate LV) and the rest PV.
>
> Since my / doesn't change much, when I add a second disk, just copy /
> and have a non-raid copy available to boot into. When I do make
> changes, just copy it over; could even make it part of the regular
> backup strategy.
raid is not a substitute for backups. It is a way to prevent downtime
and data loss due to disk failure. Preventing loss due to corruption or
user error is what backups are for. Given I can buy 250GB disks for $90
(CDN), I can't justify not using raid1 given a disk failure would
require doing a reinstall which would take much longer than I could ever
imagine being willing to work for $90, and I would rather be using my
system than doing a reinstall.
--
Len Sorensen
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