When Intel RAID controller is that? All of the ones on the
motherboard are pretty much useless if that's what you have. Those are
slower than software RAID and it's going to add driver issues you
could otherwise avoid. Better to connect the drives to the non-RAID
ports or configure the controller in JBOD mode first.
Using one of the better RAID controllers, one of Dell's good PERC
models for example, is one of the biggest hardware upgrades you could
make to this server. If your database is mostly read traffic, it
won't matter very much. Write-heavy loads really benefit from a good
RAID controller's write cache.
Actually, it is a PERC with write-cache and BBU.
ZFS will heavily use server RAM for caching by default, much more so
than UFS. Make sure you check into that, and leave enough RAM for the
database to run too. (Doing *some* caching that way is good for
Postgres; you just don't want *all* the memory to be used for that)
Right now, the size of the database is below 5GB. So I guess it will fit
into memory. I'm concerned about data safety and availability. I have
been in a situation where the RAID card went wrong and I was not able to
recover the data because I could not get an identical RAID card in time.
I have also been in a situation where the system was crashing two times
a day, and we didn't know why. (As it turned out, it was a bug in the
"stable" kernel and we could not identify this for two weeks.) However,
we had to do fsck after every crash. With a 10TB disk array, it was
extremely painful. ZFS is much better: short recovery time and it is
RAID card independent. So I think I have answered my own question - I'm
going to use ZFS to have better availability, even if it leads to poor
performance. (That was the original question: how bad it it to use ZFS
for PostgreSQL, instead of the native UFS.)
Moving disks to another server is a very low probability fix for a
broken system. The disks are a likely place for the actual failure to
happen at in the first place.
Yes, but we don't have to worry about that. raidz2 + hot spare is safe
enough. The RAID card is the only single point of failure.
I like to think more in terms of "how can I create a real-time replica
of this data?" to protect databases, and the standby server for that
doesn't need to be an expensive system. That said, there is no reason
to set things up so that they only work with that Intel RAID
controller, given that it's not a very good piece of hardware anyway.
I'm not sure how to create a real-time replica. This database is updated
frequently. There is always a process that reads/writes into the
database. I was thinking about using slony to create slave databases. I
have no experience with that. We have a 100Mbit connection. I'm not sure
how much bandwidth we need to maintain a real-time slave database. It
might be a good idea.
I'm sorry, I feel I'm being off-topic.
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