On Tue, Jun 23, 2009 at 02:51:41AM +0000, Mike Ramsey wrote: > I ran across this article "Testing Out The SSD Mode In Btrfs". > http://www.phoronix.com/scan.php?page=article&item=btrfs_ssd_mode&num=1 > > At first I was disappointed. It gave a very disappointing set of benchmarks. > However, a close reading revealed this: > > "With the OCZ Vertex SATA 2.0 SSD, which we used for this testing today, had > its > write caching always enabled. When attempting to disable the write cache > through > hdparm it would remain enabled regardless and when using sdparm it would > report > change_mode_page: failed setting page: Caching (SBC)." > > This invalidates the benchmark! Disabling the write cache would yield a 2X > improvement.
Hmmm, I'm not sure I follow. I'm guessing the write cache is critical on the vertex drives because they are using it to queue up writes into large enough units to fill an entire erasure block at once. If they took the time to put 64MB of the stuff in there, it probably does something good ;) Jens Axboe tried to reproduce the phoronix results on his ocz drive, and generally found that each run was slower than the last regardless of which mount options were used. This isn't entirely surprising, but it did make it very difficult to nail down good or bad performance. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
