Re: Mirroring Root Disks

[James Bottomley]

> Is RAID-1 only options for mirroring under Linux or something else is
> avialable.  If RAID-1 is the only option, how safe, fault tolerant it
> is. 

In practice (unless you have a three ore more SCSI channels), RAIDs 3,4,5 are 
not viable since a controller failure may take out more drives than you can 
stand to lose.  Of course, if you believe controller failures are much rarer 
than drive failures this is not a problem.

> I fear setting up RAID for root, as any problem with RAID may make
> system unbootable. Any  comments. suggestions links on Root disks
> mirroing ???? 

I've got this type of mirror boot system set up on an NCR Eagle (intel xpress 
motherboard) using software RAID 0.90 under kernel 2.2.14.  This particular 
box is ideal since it has an aic7770 dual channel SCSI controller.  The only 
real problem is setting up the system so it will still boot if one of the 
drives fails.  To do this you must maintain separate (i.e. unmirrored) /boot 
partitions for each drive and a separate lilo.conf file to install the boot 
block on each drive.  Your hardware must also be capable of booting off the 
secondary if the primary fails.

This system is primary to my business operations and has been functioning well 
for the past several months and has even overcome several boot and in-line 
drive failures (I've got old IBM scsi discs which suffer from the "sticktion" 
problem).

I can supply configuration details if you need them.

James Bottomley