On Wed, Feb 14, 2018 at 9:00 AM, Ellis H. Wilson III <ell...@panasas.com> wrote:

> Frame-of-reference here: RAID0.  Around 70TB raw capacity.  No compression.
> No quotas enabled.  Many (potentially tens to hundreds) of subvolumes, each
> with tens of snapshots.

Even if non-catastrophic to lose such a file system, it's big enough
to be tedious and take time to set it up again. I think it's worth
considering one of two things as alternatives:

a. metadata raid1, data single: you lose the striping performance of
raid0, and if it's not randomly filled you'll end up with some disk
contention for reads and writes *but* if you lose a drive you will not
lose the file system. Any missing files on the dead drive will result
in EIO (and I think also a kernel message with path to file), and so
you could just run a script to delete those files and replace them
with backup copies.

b. Variation on the above would be to put it behind glusterfs
replicated volume. Gluster getting EIO from a brick should cause it to
get a copy from another brick and then fix up the bad one
automatically. Or in your raid0 case, the whole volume is lost, and
glusterfs helps do the full rebuild over 3-7 days while you're still
able to access those 70TB of data normally. Of course, this option
requires having two 70TB storage bricks available.

Chris Murphy
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