On Oct 12, 2010, at 8:39 AM, Dan Harris wrote: > On 10/11/10 8:02 PM, Scott Carey wrote: >> would give you a 1MB read-ahead. Also, consider XFS and its built-in >> defragmentation. I have found that a longer lived postgres DB will get >> extreme >> file fragmentation over time and sequential scans end up mostly random. >> On-line file defrag helps tremendously. >> > We just had a corrupt table caused by an XFS online defrag. I'm scared > to use this again while the db is live. Has anyone else found this to > be safe? But, I can vouch for the fragmentation issue, it happens very > quickly in our system. >
What version? I'm using the latest CentoOS extras build. We've been doing online defrag for a while now on a very busy database with > 8TB of data. Not that that means there are no bugs... It is a relatively simple thing in xfs -- it writes a new file to temp in a way that allocates contiguous space if available, then if the file has not been modified since it was re-written it is essentially moved on top of the other one. This should be safe provided the journaling and storage is safe, etc. > -Dan > > -- > Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-performance -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
