Quote Originally Posted by AceNZ View Post
The performance difference is because in write back mode, the controller indicates that the write operation is complete after the data has been transferred to cache. (So you're really measuring how fast you can write to cache, not to the drives).

In write through mode, the operation isn't complete until the data has been written onto the drive(s).

This, of course, means that you should have a battery backup unit for the controller if you use write back mode and care about the integrity of your data.

This also means that the perf increase is "temporary" -- it only lasts until the write cache is full.
I dont know why, but when I copy a 10GB file from my SSD to the RAID5 I get a constant speed of 250-290MB/sec and not a constant speed of 15-19MB/sec (the cache is only 512MB)

not that I'm complaining