On Tue, Jun 23, 2009 at 3:51 AM, Mike Ramsey<MikeJRamsey@xxxxxxxxxxx> 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. > > Digging deeper, I found this: > http://www.mail-archive.com/linux-scsi@xxxxxxxxxxxxxxx/msg07949.html > > " Michael, > My information may be out of date, but last time I > looked libata didn't support MODE SELECT which is > the SCSI command to change mode page settings. > [I have sent patches several times to add support > for this in libata but ...] > > Ahhha!!! > > That looks exactly the case. > > I tested the two drives (AS and NS ones) on different > machines, and currently, NS (where things doesn't work) > is connected to AHCI controller, while the AS one is > behind mptsas. So it just looks like mptsas is doing > the right thing in the first place, while ahci (or > libata, whatever) is failing." > > So the article managed to unjustly smear both OCZ Vertex and BTRFS in one shot. allways take phoronix tests with a very big grain of salt. :-p usually they are made/prepared "with their eyes closed".. completely in the dark and they don't diagnose or try to understand the results. nevertheless, they do test stuff out... > > --Mike Ramsey > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Miguel Sousa Filipe -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
