Sebastian Kuzminsky wrote:
On 10/1/05, Christopher Smith <csmith@xxxxxxxxxxxxxxxx> wrote:
I RAID5 the drives together and glue multiple sets of 4 drives together
into a single usable chunk using LVM.
Sounds pretty cool. I've used software RAID but never LVM, let me see
if I understand your setup:
At the lowest level, you have 4-disk controller cards, each connected
to a set of 4 disks. Each set of 4 has a software RAID-5. All the
RAID-5 arrays are used as LVM physical volumes. These PVs are part of
a single volume group, from which you make logical volumes as needed.
When you want more disk, you buy 4 big modern disks (and a 4x
controller if needed), RAID-5 them, extend the VG onto them, and
extend the LV(s) on the VG. Then I guess you have to unmount the
filesystem(s) on the LV(s), resize them, and remount them.
If you get low on room in the case or it gets too hot or noisy, you
have to free up an old, small RAID array. You unmount, resize, and
remount the filesystem(s), reduce the LV(s) and the VG, and then
you're free to pull the old RAID array from the case.
Yep, that's pretty much bang on. The only thing you've missed is using
pvmove to physically move the data off the soon-to-be-decomissioned
PVs(/RAID arrays).
Be warned, for those who haven't used it before, pvmove is _very_ slow.
Apart from the actual hardware installations and removals, the various
reconfigurations have been quite smoothe and painless, with LVM allowing
easy migration of data to/from RAID devices, division of space, etc.
I've had 3 disk failures, none of which have resulted in any data loss.
The "data store" has been moved across 3 very different physical
machines and 3 different Linux installations (Redhat 9 -> RHEL3 -> FC4).
Your data survives one disk per PV croaking, but two disks out on any
one PV causes complete data loss, assuming you use the stripe mapping.
Yep, that's correct. I've never lost more than one disk out of an array
at once and I've always replaced any disk failures the same day. I lost
two of the 40GB drives (about 6 months apart - back before I had decent
cooling on them) and one of the 120GB drives.
You use SATA, which does not support SMART yet, right? So you get no
warning of pending drive failures yet.
Yep. The only annoyance. I eagerly await the ability to check my SATA
disks with SMART.
CS
-
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
