Jason Tower wrote:
i'm sure someone can find my old post(s), but there are three major
problems with software raid:
1. the bootloader is installed on the MBR of the first disk only. if
that disk goes bye bye you're in trouble. sure, you can install
lilo/grub on multiple MBRs but that's a pita and an inelegant solution.
2. some sata chipsets flat out don't work with software raid 5, they
will crash the system hard either during initialization or under heavy
i/o. i've personally seen this happen on no less than three totally
different systems with multiple distros.
3. if a disk dies suddenly, the system is gonna crash regardless of raid
because the kernel can no longer communicate with /dev/sdx, it just
disappears. go ahead, set up software raid with hot swap disks then
yank one out while the system is running, see what happens. the data
itself is probably ok (you'll have a degraded array upon reboot) but
availability is shot. plus your fstab may no longer be accurate once a
disk is removed.
there are probably workaround for these issues, or if they don't bother
you then knock yourself out with software raid. i use it myself if
circumstances justify it. but i've built enough systems to know that
hardware raid exists for a reason. if you want to do the job right get
a 3ware card and sleep peacefully.
jason
Jason,
As per number one, here is how you write to /dev/md0, /dev/hda and
/dev/hdc in lilo. It's straight from the software raid docs.
boot=/dev/md0
root=/dev/md0
#this writes the boot signatures to either disk.
raid-extra-boot=/dev/hda,/dev/hdc
image=/vmlinuz
label=RAID
read-only
As far as whether to do raid5 in software, I haven't done it.
I do trust mdadm to do raid1.
Matt
--
TriLUG mailing list : http://www.trilug.org/mailman/listinfo/trilug
TriLUG Organizational FAQ : http://trilug.org/faq/
TriLUG Member Services FAQ : http://members.trilug.org/services_faq/
