[Beowulf] Re: Beowulf Storage Node

[John Hearns]

2009/4/15 Matt Lawrence <matt at technoronin.com>:
> >
> Well, that's not quite the same as grub being able to actually speak RAID,
> but it is useful if you can afford to dedicate the space.  Typically I want
> my drives in a RAD6 and would prefer not to carve off a chunk of all the
> drives to use as a RAID1.  For typical 1U servers, then RAID1 is the way to
> go, there's often only two drives available.
>
I politely disagree.
We always built cluster head nodes with a mirrored disk pair for the
systems disk, and a RAID 5 or 6 set with the rest of the disks in the
chassis.
If possible, you want a sensibly sized disk for your system disk -
IMHO running terabyte-sized SATA drives as the OS drives on a system
is inviting trouble. Get something small enough that you can readily
back it up, and make sure it is mirrored.
Then let the big data store look after itself - format it with XFS,
run LVM on it, run RAID 6 on it.
And if the worst happens and you lose your system disks, or indeed
more likely you want to do a systems update,
you UNLATCH A DRIVE AND PUT IT ON THE SHELF. Then you merrily
update/patch/generally fool with the other drive (plus a replacement
spare) and you have an instant fallback plan if things go pear-shaped.
Sorry - I just don't buy having a RAID6 across all disks in one
chassis. Unless you are booting over a SAN or something.