В Пн., 29/08/2011 в 16:11 +0200, Paul Reeves пишет: > The levels are > > Application - we can set FW=ON or OFF. If ON the we are saying write > everything to disc immediately. If FW=OFF then we see a massive performance > gain on small test runs (especially if super* is used.) > > Filesystem - ext3 (and others) are mounted async by default (at least for > opensuse). I've done disc i/o tests with the partition mounted async that > show > anomalies for disc iops. The only way to remove the anomalies was with > mounting with sync. I had previously mounted with barrier=1 but that was > insufficent. (Of course FW=ON). >
It seems that you've got slightly strange results here. From what I've always noticed sync/async in mount specify default behaviour, where async may be overridden using O_SYNC in open(). For example - if you mount a disk with database shadow sync, shadow will be OK after power failure even when primary database file is corrupted. I've seen this effect many times in one funny environment, where UPS used to turn of all power for unknown reason. ------------------------------------------------------------------------------ EMC VNX: the world's simplest storage, starting under $10K The only unified storage solution that offers unified management Up to 160% more powerful than alternatives and 25% more efficient. Guaranteed. http://p.sf.net/sfu/emc-vnx-dev2dev Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
