Thread: Upgrade OS from Redhat AS3 (2.4 kernel) to AS4 (2.6) - Advice on keeping PG happy?

Roger Hand wrote:

> Due to performance issues (which I wrote about on pg-performance list)
> we will be upgrading our Redhat AS3.0 box (kernel 2.4) to Redhat AS4
> (kernel 2.6) in order to take advantage of the better I/O that the 2.6
> kernel offers. (I say upgrading but actually we'll wipe the box and
> start fresh.)
>
> We are running Postgres 8.0.3.
>
> I had assumed we would have to backup/restore the entire db, but I got
> to wondering if it would be possible to simply point the new Postgres
> install to the existing db (the data itself is on a separate drive
> array) and be back up and running without the time to do the restore.


Yes as long as you are not switching architectures (say to x86_64) or
filesystems you should be fine. I assume you will be running 8.0.3
on the new system as well.

>
> Is this a relatively simple matter? Or is it too hazardous and tricky
> to bother with?

Not hazardous at all as long as you don't accidently format the
filesystem ;). Make a tar backup just in case.

>
> If it's possible I'd appreciate a list of what I'd need to save off
> the old drive, where the os and Postgres program itself lived.

Nothing. The postgresql.conf and pg_hba.conf will reside in the data
directory so it will be fairly independent. Note
that I am ONLY talking about postgres here. You may want to save things
from the OS for other reasons.

>
> Also: Anything to watch out for with Postgres on 2.6 kernel as opposed
> to 2.4? Any settings that should be different? We've been advised to
> try "elevator=deadline". We write pretty much 24 hours a day, and have
> I/O issues!

Well 2.6 is pretty solid but I wasn't part of the thread so I can't tell
you if this will solve your problem. I can
say that overall 2.6 is much better for databases.

Sincerely,

Joshua D. Drake
Command Prompt, Inc.



>
> -Roger

"Joshua D. Drake" <jd@commandprompt.com> writes:
> Roger Hand wrote:
>> I had assumed we would have to backup/restore the entire db, but I got
>> to wondering if it would be possible to simply point the new Postgres
>> install to the existing db (the data itself is on a separate drive
>> array) and be back up and running without the time to do the restore.

> Yes as long as you are not switching architectures (say to x86_64) or
> filesystems you should be fine. I assume you will be running 8.0.3
> on the new system as well.

It has to be the same machine architecture, same major Postgres version
(8.0.something), and mostly the same configure options (eg, you can't
change your mind about --enable-integer-datetimes).

Good idea to take a pg_dump backup beforehand anyway, just in case.

            regards, tom lane