From mboxrd@z Thu Jan 1 00:00:00 1970 From: Miguel F Mascarenhas Sousa Filipe Subject: Re: Phoronix article slaming BTRFS Date: Tue, 23 Jun 2009 11:13:12 +0100 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: linux-btrfs@vger.kernel.org To: Mike Ramsey Return-path: In-Reply-To: List-ID: On Tue, Jun 23, 2009 at 3:51 AM, Mike Ramsey w= rote: > I ran across this article "Testing Out The SSD Mode In Btrfs". > http://www.phoronix.com/scan.php?page=3Darticle&item=3Dbtrfs_ssd_mode= &num=3D1 > > At first I was disappointed. =C2=A0It gave a very disappointing set o= f benchmarks. > However, a close reading revealed this: > > "With the OCZ Vertex SATA 2.0 SSD, which we used for this testing tod= ay, had its > write caching always enabled. When attempting to disable the write ca= che through > hdparm it would remain enabled regardless and when using sdparm it wo= uld 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@vger.kernel.org/msg07949.html > > " Michael, > =C2=A0My information may be out of date, but last time I > =C2=A0looked libata didn't support MODE SELECT which is > =C2=A0the SCSI command to change mode page settings. > =C2=A0[I have sent patches several times to add support > =C2=A0for 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. =C2=A0So 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@vger.kernel.org > More majordomo info at =C2=A0http://vger.kernel.org/majordomo-info.ht= ml > --=20 Miguel Sousa Filipe -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" = in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html