PostgreSQL 3.3 on gjournaled fs

[Ivan Voras]

Axel Rau wrote:
> Hi,
> 
> I'm starting migration of my PostgreSQL tablespaces to gjournaled fs on 
> 7-stable.
> Dedicated box is Opteron with Areca.
> Any experiences or hints?
> 4GB journal provider?

The question is - why do you need gjournal? PostgreSQL (and other decent 
databases) does its own journaling (search for WAL), so using it on a 
journaled file system doesn't do much.

If you really want it, it won't hurt you. Journal size needs to be 
scaled based on your load. If you have constant writes you need a larger 
journal. You need it to hold 20*(write_rate in MB/s) megabytes. E.g. if 
your array does 100 MB/s, you need a 2000 MB journal. This calculation 
is for default gjournal settings.

You could put the journal on another drive or array for best 
performance. (Of course, you could skip gjournal and put the WAL on the 
other drive).


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