Date: Fri, 30 Jun 2006 11:57:05 +0800 From: "Leo Huang" <leo.huang.gd@gmail.com> To: "Bruce Evans" <bde@zeta.org.au> Cc: freebsd-fs@freebsd.org, Ivan Voras <ivoras@fer.hr> Subject: Re: Is the fsync() fake on FreeBSD6.1? Message-ID: <a0cd7c070606292057p6f120ef6mb45533217a4d93db@mail.gmail.com> In-Reply-To: <20060629201157.N77878@delplex.bde.org> References: <a0cd7c070606270032h3a42de6ahf21cd11abedb6400@mail.gmail.com> <44A1B958.4030204@fer.hr> <20060628230439.M75051@delplex.bde.org> <a0cd7c070606281920r34fcc9dfr241ae6ac662024e4@mail.gmail.com> <20060629201157.N77878@delplex.bde.org>
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hi, Bruce > How did you disable "driver" write caching? I think both Bjorn and I > meant the _drive_ write caching, and that is what you refer to as "disk" > write caching. Only turn off the caching in the lowest layer (disk == > drive). Yes, "disk" what I say means drive. On FreeBSD, I use camcontrol to disable the drive write caching. Enable: mysql-test-4# camcontrol modepage da0 -m8 IC: 0 ABPF: 0 CAP: 0 DISC: 1 SIZE: 0 WCE: 1 MF: 0 RCD: 0 Demand Retention Priority: 0 Write Retention Priority: 0 Disable Pre-fetch Transfer Length: 65535 Minimum Pre-fetch: 0 Maximum Pre-fetch: 0 Maximum Pre-fetch Ceiling: 65535 Disable: mysql-test-4# camcontrol modepage da0 -m8 IC: 0 ABPF: 0 CAP: 0 DISC: 1 SIZE: 0 WCE: 0 MF: 0 RCD: 0 Demand Retention Priority: 0 Write Retention Priority: 0 Disable Pre-fetch Transfer Length: 65535 Minimum Pre-fetch: 0 Maximum Pre-fetch: 0 Maximum Pre-fetch Ceiling: 65535 On Debian, I use sginfo to disable it. Enable: mysql-test-1:/home/huangjy# sginfo -c /dev/sda Caching mode page (0x8) ----------------------- Initiator Control 0 ABPF 0 CAP 0 DISC 1 SIZE 0 Write Cache Enabled 1 MF 0 Read Cache Disabled 0 Demand Read Retention Priority 0 Demand Write Retention Priority 0 Disable Pre-fetch Transfer Length 65535 Minimum Pre-fetch 0 Maximum Pre-fetch 0 Maximum Pre-fetch Ceiling 65535 FSW 1 LBCSS 0 DRA 0 Number of Cache Segments 8 Cache Segment size 0 Non-Cache Segment size 0 Disable: mysql-test-1:/home/huangjy# sginfo -c /dev/sda Caching mode page (0x8) ----------------------- Initiator Control 0 ABPF 0 CAP 0 DISC 1 SIZE 0 Write Cache Enabled 0 MF 0 Read Cache Disabled 0 Demand Read Retention Priority 0 Demand Write Retention Priority 0 Disable Pre-fetch Transfer Length 65535 Minimum Pre-fetch 0 Maximum Pre-fetch 0 Maximum Pre-fetch Ceiling 65535 FSW 1 LBCSS 0 DRA 0 Number of Cache Segments 8 Cache Segment size 0 Non-Cache Segment size 0 > I wonder when all drives will have enough fast enough nonvolatile RAM for > write caching to just work. Our test computer only have one scsi disk. So I think that the data in drive write caching will be lost when the power is off. Regards, Leo Huang 2006/6/29, Bruce Evans <bde@zeta.org.au>: > On Thu, 29 Jun 2006, Leo Huang wrote: > > >> >> OS Clients Result(queries per second) TPS(got from > >> >> iostat) > >> >> FreeBSD6.1 50 516.1 about 2000 > >> > >> Seems normal for drives that do write caching. > > > > I disable the driver write caching as Bjorn Gronvall suggest, the > > result show that the TPS come down to about 200. So I think you and > > Bjorn Gronvall are right. It is the disk write caching make the TPS so > > high. > > > >> >> Debian3.1 50 49.8 about 200 > >> > >> Seems to slow for disks that do write caching. Maybe Debian does something > >> to force the drive to complete it's i/o, or just does a full sync() like > >> someone mentioned Linux doing. > > > > I use sginfo the find that the disk write caching is also enabled > > default. After the disk write caching is disabled, the TPS also come > > down from 200 to 110. This is really pullze me. Can you give me more > > infomation about it? > > How did you disable "driver" write caching? I think both Bjorn and I > meant the _drive_ write caching, and that is what you refer to as "disk" > write caching. Only turn off the caching in the lowest layer (disk == > drive). > > I wonder when all drives will have enough fast enough nonvolatile RAM for > write caching to just work. > > Bruce >
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