Ron Mayer wrote: > Bruce Momjian wrote: > > Greg Smith wrote: > >> Bruce Momjian wrote: > >>> I have added documentation about the ATAPI drive flush command, and the > >> > >> If one of us goes back into that section one day to edit again it might > >> be worth mentioning that FLUSH CACHE EXT is the actual ATAPI-6 command > >> that a drive needs to support properly. I wouldn't bother with another > >> doc edit commit just for that specific part though, pretty obscure. > > > > That setting name was not easy to find so I added it to the > > documentation. > > If we're spelling out specific IDE commands, it might be worth > noting that the corresponding SCSI command is "SYNCHRONIZE CACHE"[1]. > > > Linux apparently sends FLUSH_CACHE commands to IDE drives in the > exact sample places it sends SYNCHRONIZE CACHE commands to SCSI > drives[2]. > > It seems that the same file systems, SW raid layers, > virtualization platforms, and kernels that have a problem > sending FLUSH CACHE commands to SATA drives have he same exact > same problems sending SYNCHRONIZE CACHE commands to SCSI drives. > With the exact same effect of not getting writes all the way > through disk caches.
I always assumed SCSI disks had a write-through cache and therefore didn't need a drive cache flush comment. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com PG East: http://www.enterprisedb.com/community/nav-pg-east-2010.do -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
