Re: Install Postgres on a SAN volume?

Thanks.

I notice that the link you provided says:
"Per best practices, my postgres data directory, xlogs and WAL archives
are on different filesystems (ZFS of course). "

Why is this a best practice?  Is there a reference for that?

Greg Smith wrote:
> On Mon, 8 Sep 2008, William Garrison wrote:
>
>> 2) We could install PostgreSQL onto the C: drive and then configure
>> the data folder to be on the SAN volume (Z:)
>
> Do that.  You really don't want to get into the situation where you
> can't run anything related to the PostgreSQL service just because the
> SAN isn't available.  You may have internal SAN fans that will swear
> that never happens, but it does.  Also, it allows installing a later
> PostgreSQL version upgrade on another system and testing against the
> SAN data files in a way that said system could become the new server.
> There's all kinds of systems management reasons you should separate
> the database application from the database files.
>
>> So I am assured it is fast.
>
> Compared to what?  The same amount spent on direct storage would be
> widly faster.
>
> The thing to remember about SANs is that they are complicated, and
> there are many ways you can misconfigure them so that their database
> performance sucks.  Make sure you actually benchmark the SAN and
> compare it to direct connected disks to see if it's acting sanely;
> don't just believe what people tell you.
>
> I personally can't understand why anybody would spend SAN $ and then
> hobble the whole thing by running PostgreSQL on Windows.  The Win32
> port is functional, but it's really not fast.
>
>> It is really nice because it supports instant snapshots so we can, in
>> theory, snapshot a volume and re-mount it elsewhere.
>
> You'll still need to setup basic PITR recovery to know you got a
> useful snapshot.  See
> http://lethargy.org/~jesus/archives/92-PostgreSQL-warm-standby-on-ZFS-crack.html
> for a nice intro to that that uses ZFS as the snapshot implementation.
>
> --
> * Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD
>