Thread: DOC: Wal update
I add few sentences how to write cache works on Solaris platform.
Zdenek
Index: doc/src/sgml/wal.sgml
===================================================================
RCS file: /zfs_data/cvs_pgsql/cvsroot/pgsql/doc/src/sgml/wal.sgml,v
retrieving revision 1.49
diff -c -r1.49 wal.sgml
*** doc/src/sgml/wal.sgml 10 Dec 2007 22:08:36 -0000 1.49
--- doc/src/sgml/wal.sgml 11 Dec 2007 14:22:32 -0000
***************
*** 65,71 ****
write caching. On <productname>FreeBSD</> use
<application>atacontrol</>. (For SCSI disks use <ulink
url="http://sg.torque.net/sg/sdparm.html"><application>sdparm</></ulink>
! to turn off <literal>WCE</>.) On <productname>Windows</> write caching is
disabled by unchecking <literal>My Computer\Open\{select disk
drive}\Properties\Hardware\Properties\Policies\Enable write caching on
the disk</>.
--- 65,73 ----
write caching. On <productname>FreeBSD</> use
<application>atacontrol</>. (For SCSI disks use <ulink
url="http://sg.torque.net/sg/sdparm.html"><application>sdparm</></ulink>
! to turn off <literal>WCE</>.) On <productname>Solaris</> with UFS write cache
! is disabled by default. Use <command>format -e</> to control it. ZFS works correctly
! with enabled write cache. On <productname>Windows</> write caching is
disabled by unchecking <literal>My Computer\Open\{select disk
drive}\Properties\Hardware\Properties\Policies\Enable write caching on
the disk</>.
Zdenek Kotala wrote: > I add few sentences how to write cache works on Solaris platform. I have updated our documentation with the attached patch. I was able to verify all the information in this change. I changed your original wording because the statement that UFS turns off write cache seemed unclear because the file system seems independent of the disk write cache. (What happens if you have UFS and ZFS on the same drive?) Anyway I think the attached wording is fine. -- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB http://postgres.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + Index: doc/src/sgml/wal.sgml =================================================================== RCS file: /cvsroot/pgsql/doc/src/sgml/wal.sgml,v retrieving revision 1.51 diff -c -c -r1.51 wal.sgml *** doc/src/sgml/wal.sgml 16 Dec 2007 14:05:12 -0000 1.51 --- doc/src/sgml/wal.sgml 29 Dec 2007 17:53:58 -0000 *************** *** 65,74 **** write caching. On <productname>FreeBSD</> use <application>atacontrol</>. (For SCSI disks use <ulink url="http://sg.torque.net/sg/sdparm.html"><application>sdparm</></ulink> ! to turn off <literal>WCE</>.) On <productname>Windows</> if ! <varname>wal_sync_method</> is <literal>open_datasync</> (the default), ! write caching is disabled by unchecking <literal>My ! Computer\Open\{select disk drive}\Properties\Hardware\Properties\Policies\Enable write caching on the disk</>. Also on Windows, <literal>fsync</> and <literal>fsync_writethrough</> never do write caching. --- 65,78 ---- write caching. On <productname>FreeBSD</> use <application>atacontrol</>. (For SCSI disks use <ulink url="http://sg.torque.net/sg/sdparm.html"><application>sdparm</></ulink> ! to turn off <literal>WCE</>.) On <productname>Solaris</> the disk ! write cache is controlled by <ulink ! url="http://www.sun.com/bigadmin/content/submitted/format_utility.jsp"><literal>format ! -e</></ulink>. (The Solaris <acronym>ZFS</> file system is safe with ! disk write-cache enabled because it issues its own disk cache flush ! commands.) On <productname>Windows</> if <varname>wal_sync_method</> ! is <literal>open_datasync</> (the default), write caching is disabled ! by unchecking <literal>My Computer\Open\{select disk drive}\Properties\Hardware\Properties\Policies\Enable write caching on the disk</>. Also on Windows, <literal>fsync</> and <literal>fsync_writethrough</> never do write caching.
Bruce Momjian wrote: > Zdenek Kotala wrote: >> I add few sentences how to write cache works on Solaris platform. > > I have updated our documentation with the attached patch. I was able to > verify all the information in this change. Thanks. > I changed your original wording because the statement that UFS turns off > write cache seemed unclear because the file system seems independent of > the disk write cache. (What happens if you have UFS and ZFS on the same > drive?) You are right UFS does not modify (write) cache setting and it is usually disabled by default on most disks. If ZFS and UFS are on same disk, than ZFS don't enable disk cache. It is a reason why put ZFS on separate disk is better. See http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide#Storage_Pools > Anyway I think the attached wording is fine. Yes, it is. Zdenek PS: There are some articles about ZFS. http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide http://www.solarisinternals.com/wiki/index.php/ZFS_Evil_Tuning_Guide http://www.solarisinternals.com/wiki/index.php/ZFS_for_Databases
Zdenek Kotala wrote: > Bruce Momjian wrote: > > Zdenek Kotala wrote: > >> I add few sentences how to write cache works on Solaris platform. > > > > I have updated our documentation with the attached patch. I was able to > > verify all the information in this change. > > Thanks. > > > I changed your original wording because the statement that UFS turns off > > write cache seemed unclear because the file system seems independent of > > the disk write cache. (What happens if you have UFS and ZFS on the same > > drive?) > > You are right UFS does not modify (write) cache setting and it is usually > disabled by default on most disks. If ZFS and UFS are on same disk, than ZFS > don't enable disk cache. It is a reason why put ZFS on separate disk is better. See > http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide#Storage_Pools > > > Anyway I think the attached wording is fine. > > Yes, it is. > > Zdenek > > PS: There are some articles about ZFS. > > http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide > http://www.solarisinternals.com/wiki/index.php/ZFS_Evil_Tuning_Guide > http://www.solarisinternals.com/wiki/index.php/ZFS_for_Databases > > ---------------------------(end of broadcast)--------------------------- > TIP 3: Have you checked our extensive FAQ? > > http://www.postgresql.org/docs/faq -- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB http://postgres.enterprisedb.com + If your life is a hard drive, Christ can be your backup. +