On Tue, Nov 10, 2009 at 3:05 PM, Ivan Voras <ivoras@xxxxxxxxxxx> wrote: > Laurent Laborde wrote: >> >> Hi ! >> We recently had a problem with wal archiving badly impacting the >> performance of our postgresql master. > > Hmmm, do you want to say that copying 16 MB files over the network (and > presumably you are not doing it absolutely continually - there are pauses > between log shipping - or you wouldn't be able to use bandwidth limiting) in > an age when desktop drives easily read 60 MB/s (and besides most of the file > should be cached by the OS anyway) is a problem for you? Slow hardware? > > (or I've misunderstood the problem...) Desktop drive can easily do 60MB/s in *sequential* read/write. We use high performance array of 15.000rpm SAS disk on an octocore 32GB and IO is always a problem. I explain the problem : This server (doing wal archiving) is the master node of the over-blog's server farm. hundreds of GB of data, tens of millions of articles and comments, millions of user, ... ~250 read/write sql requests per seconds for the master ~500 read sql request per slave. Awefully random access overload our array at 10MB/s at best. Of course, when doing sequential read it goes to +250MB/s :) Waiting for "cheap" memory to be cheap enough to have 512Go of ram per server ;) We tought about SSD. But interleaved read/write kill any SSD performance and is not better than SSD. Just more expensive with an unknown behaviour over age. -- ker2x sysadmin & DBA @ http://www.over-blog.com/ -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
