[Gluster-users] Advice for sizing a POC

[Jake Davis]

Greetings, I'm trying to spec hardware for a proof of concept. I'm hoping
for a sanity check to see if I'm asking the right questions and making the
right assumptions.
I don't have real numbers for expected workload, but for our main use case,
we're likely talking a few hundred thousand files, read heavy, with average
file size around 1 GB. Fairly parallel access pattern.

I've read elsewhere that the max recommended disk count for a RAID6 array
is twelve. Is that per node, or per brick? i.e. if I have a number of 24 or
36 disk arrays attached to a single node, would it make sense to divide the
larger array into 2 or 3 bricks with 12 disk stripes, or do a want to limit
the brick count to one per node in this case?

For FUSE clients, assuming one 12 disk RAID6 brick per node, in general,
how many nodes do I need in my cluster before I start meeting/exceeding the
throughput of a direct attached raid via NFS mount?

RAM; is it always a case of the more, the merrier? Or is there some rule of
thumb for calculating return on investment there?

Is there a scenario were adding a few SSD's to a node can increase the
performance of a spinning disk brick by acting as a read cache or some
such? Assuming non-ZFS.

I've read that for highly parallel access, it might make more sense to use
JBOD with one brick per disk. Is that advice file size dependent? And What
question do I need to ask myself to determine how many of these single disk
bricks I want per-node?

Many thanks!
-Jake
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