Install and RAID
RAID is vitally important for serious machines. This means all server-type
machines and workstations for people who do important work.
I would like to develop new installation software to allow Debian to be
installed to RAID1 arrays.
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.
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.
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!
So the question is, is it worth still allowing installation to non-RAID
partitions?
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.
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.
What do you think?
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