Re: Installing Debian + RAID
What about using LVM to create a virtual disk the sum of the
partitions? Has anyone had experience with this?
Cyan
On Thu, Aug 23, 2001 at 03:47:51PM +0300, George Karaolides wrote:
>
> On Thu, 23 Aug 2001 daniel.weller@orf.at wrote:
>
> > My question is whether it would be possible to install Debian onto a
> > software RAID (which is not in place at the moment because NTFS partitions
> > are covering 2 out of 3 harddisks) and how that would work.
>
> It is absolutely possible; I have put the servers at work on Debian with
> the root filesystem on RAID 5.
>
> > I thought of creating a small ext2 partition mounted as /boot and then
> > having one linear RAID mounted as / - would this be a good idea?
>
> It would certainly work, but as to it being a good idea, it has rather
> more chances of failure than a single disk. A failure on either disk
> would trash the filesystem.
>
> > I've never had any harddisk crashes
>
> Have you heard of a Mr. Murphy and his law? You're going to have a disk
> crash when you've finished installing your new linear RAID, and have been
> using it long enough for some important data to accumulate. Nad what
> about cables going wonky or coming loose etc.? In a single-disk system,
> this will often only bring the system down; with a linear device, it can
> trash the whole filesystem as the devices go out of sync.
>
> I would suggest that a much better idea than using your two (I presume
> non-identical) disks as a linear array is to use them as a JBOD (Just A
> Bunch Of Disks) setup. Just install a basic system on one of them,
> partition the other one and mount those partitions as /usr/local, /home
> and so on before completing the install. This will give you improved
> performance as the system will read data files and system files from two
> disks, and if the /home disk conks out you just replace it and restore the
> user files from backup. If the system disk conks out you won't be any
> worse off than you would be after a disk crash on a single-disk system.
>
> > how do I create it prior to installing Debian?
>
> I haven't done it myself, but I'm fairly certain that you must have a
> spare disk or partition available which will in the end *not* be a part of
> the linear device on which the root fs will be. You will make a scratch
> install of a basic system on that, use it to create the linear device,
> copy the system to it, make the device bootable and then complete the
> install with all your required software. Incidentally, this is unlike
> RAID 1, 4 or 5, where with the new raidtools you can use the failed-disk
> directive to include the device with the initial install in the RAID
> array.
>
> All things considered, I wouldn't bother with linear mode. It offers no
> advantage besides concatenating two devices to make a bigger filesystem.
> This I think was only relevant in the days when you had to concatenate two
> disks to get the 400 Megs you needed for a /usr filesystem big enough for
> X Window. I don't think it's relevant today.
>
> George Karaolides 8, Costakis Pantelides St.,
> tel: +35 79 68 08 86 Strovolos,
> email: george@karaolides.com Nicosia CY 2057,
> web: www.karaolides.com Republic of Cyprus
>
>
>
>
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