There are various conditions to doing this safely which, if not properly
understood, can lead to problems very much worse than the cure.
1) Even hardware RAID caches a lot of indices and the like in volitile RAM
(it's a performance issue). Depending on implementation this may either be
system RAM or RAM built into the controller itself. The issue is that a
catastrophic power failure will certainly lead to the array being left in an
unuseable (corrupted) state. The simple answer, of course is to never use
RAID unless the entire system is powered by a UPS, with at least 15 minutes
of run-time after power-fail, and use of powerd or similar power-fail
shutdown procedures.
2) Synchronization of array components is a bit tricky when files are open.
This is vastly complicated when the array is also a bootable partition. In
production systems, I usually have two separate array controllers, one for
boot and the other for applications. I usually try to make the boot
partition read-only. There are also security considerations associated with
this architecture.
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of Amias Channer
> Sent: Thursday, November 25, 1999 5:52 AM
> To: Linux-Raid
> Cc: [EMAIL PROTECTED]
> Subject: Booting from RAID
>
>
> Hello all ,
>
> I have heard people mentioning that running the OS on a RAID
> device is a
> bad idea , why is this ?
> We have an external SCSI raid controller that presents itself to the
> system as a SCSI hard drive (/dev/sda)
> Would i be right in assuming that putting the OS on this is not a
> problem as the RAID functionality
> is not controlled by the computer and that it would only be a
> problem if
> the RAID was controlled by the OS ?
>
> Thanks in Advance
>
> Toodle-pip
> Amias
>
