Re: "PANIC: could not open critical system index 2662" - twice

> No idea about the former, but bad hardware is a good enough explanation.
> As to keeping it from happening: use good hardware.

Alright, thanks, I'll just keep my fingers crossed that it doesn't
happen again then!

> Also: Use checksums. PostgreSQL offers data checksums[1]. Some
filesystems also offer checksums.

We have data_checksums=on. (It must be on by default, since I cannot
find that in our config files anywhere.) However, the docs say "Only
data pages are protected by checksums; internal data structures and
temporary files are not.", so I guess pg_class_oid_index might be an
"internal data structure"?

We also have checksum=on for the ZFS dataset on which the data is stored
(also the default - we didn't change it). ZFS did detect problems (zpool
status reported read, write and checksum errors for one of the old
disks), but it also said "errors: No known data errors". I understood
that to meant that it recovered from the errors, i.e. wrote the data
different disk blocks or read it from another disk in the pool.