On Tue, Jul 18, 2006 at 10:37:35AM -0700, Richard Elling wrote:
> Daniel,
> When we take into account time, the models we use are Markov models
> which consider the amount of space used, disk size, block and whole
> disk failures, RAID scheme, recovery from tape time, spares, etc.
> All of these views of the system are being analyzed. Needless to say,
> with the zillions of permutations of RAID schemes possible with a
> system such as the Sun Fire X4500, we'll never model all of them.
> Hence my request for the popular configs which I will model in detail.
My two cents -
One thing I would pay attention to is the future world of native ZFS
root. On a thumper, you only have two drives which are bootable from
the BIOS. For any application in which reliability is important, you
would have these two drives mirrored as your root filesystem. There can
be no hot spares for this pool, because any device you hot spare in will
not be readable from the BIOS.
So, you should assume that for any RAID configuration, you're going to
have a mirror of c3t0 and c3t4 (disks 0 and 1) as your root pool, with
the remaining 46 disks available for user data. The loss of both root
disks would imply that the system becomes unavailable, but wouldn't
necessarily result in loss of user data. If the model supports
distinguishing these two outcomes, it could potentially cover such
things as motherboard failure or controller failure, which would bring
the system down but would not result in loss of data. A truly complete
model would also take into account the loss of fans (thumper has 5x2
fans covering 12 rows of disks), though I doubt that anyone has any
reliable data on the effect of running with only one fan in a redundant
group.
For all the Thumper raidz2 models, I would assume only having 46 disks.
This gives a nice bias towards one of the following configurations:
- 5x(7+2), 1 hot spare, 21.0TB
- 4x(9+2), 2 hot spares, 18.0TB
- 6x(5+2), 4 hot spares, 15.0TB
The performance characteristics of these configurations would be equally
interesting.
- Eric
--
Eric Schrock, Solaris Kernel Development http://blogs.sun.com/eschrock
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