On Wed, 2006-08-09 at 16:11, Steve Poe wrote: > Jim, > > I'll give it a try. However, I did not see anywhere in the BIOS > configuration of the 642 RAID adapter to enable writeback. It may have > been mislabled cache accelerator where you can give a percentage to > read/write. That aspect did not change the performance like the LSI > MegaRAID adapter does.
Nope, that's not the same thing.
Does your raid controller have batter backed cache, or plain or regular cache? write back is unsafe without battery backup.
The default is write through (i.e. the card waits for the data to get written out before acking an fsync). In write back, the card's driver writes the data to the bb cache, then returns on an fsync while the cache gets written out at leisure. In the event of a loss of power, the cache is flushed on restart.