Re: Install and RAID
On Sat, Jan 20, 2001 at 03:17:15PM +1100, Russell Coker wrote:
> RAID is vitally important for serious machines. This means all server-type
> machines and workstations for people who do important work.
I do agree.
> I would like to develop new installation software to allow Debian to be
> installed to RAID1 arrays.
Ohh I'm about to do it myself. I have tracked down the code so now the
implementation may start.
> One problem with this is that the RAID-1 sync process (which occurs when the
> RAID array is initialised) takes a large amount of time and makes all disk
> access very slow (can take 2 hours or more).
> So we don't really want a RAID-1 sync operation to occur while the main
> software installation is in progress.
Do this really occur if you format the raided partition? I have not
had this problem myself anyway.
> To solve this I believe that it is best to create a RAID-1 array in "degraded
> mode" (basically telling the system that one drive has failed). This makes
> the system operate and perform as if it was a single disk not a RAID array.
> Then after the main install has completed the system could be instructed to
> go into full RAID mode and sync the disks.
Isn't it better to partition the disk and then format it, so that it do not
have to sync at all? But you might of course have had problems that I have
not noticed.
> Now if we do this then someone who only has a single hard drive may as well
> go through the RAID install process and just skip the second stage of turning
> on the RAID. Then if at some future time (months or years later) they
> purchased a second hard drive then RAID mirroring could easily be turned on!
That is a good thing. Is that really possible and if it is that can be
very interesting.
> So the question is, is it worth still allowing installation to non-RAID
> partitions?
Err. I do not think I understand this question.
> A RAID partition is the same as a regular partition apart from having a small
> amount (less than 100K) of disk space reserved at the end.
>
> If you choose to not use the RAID device you can just edit /etc/fstab to
> refer to the raw devices instead and change the partition type to something
> other than 0xFD, and reboot.
Yes and you probably do not even have to reboot, just remount.
> In this scheme if the user sets partitions as type 0xFD then it will install
> as RAID and start RAID at every boot.
>
> If the user sets partitions as other types then it would install as RAID but
> put the raw devices into /etc/fstab. So the RAID driver would not be used at
> boot, but this could easily be changed without requiring a rebuild.
Why not use it at boot? Lilo do allow that, so that should be no prob.
Sounds interesting. By the way see my question (some days ago on this list)
and see it that can be something interesting.
We use raid at work but it is quite tricky to install it.
// Ola
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