Thread: symlinking pg_xlog
Hi, due to I/O-bottle necks I think of making a symlink from pg_xlog to another physical disk. This is a modification inside the cluster dir. What kind of idea is that? bad one?
On Fri, Jun 24, 2005 at 03:18:12PM +0200, KÖPFERL Robert wrote: > > due to I/O-bottle necks I think of making a symlink from pg_xlog to another > physical disk. > This is a modification inside the cluster dir. What kind of idea is that? > bad one? See the "Write-Ahead Logging (WAL)" chapter in the documentation: http://www.postgresql.org/docs/8.0/static/wal-internals.html "It is of advantage if the log is located on another disk than the main database files. This may be achieved by moving the directory pg_xlog to another location (while the server is shut down, of course) and creating a symbolic link from the original location in the main data directory to the new location." Several third-party performance-tuning documents make the same recommendation. -- Michael Fuhr http://www.fuhr.org/~mfuhr/
=?iso-8859-1?Q?K=D6PFERL_Robert?= <robert.koepferl@sonorys.at> writes:
> due to I/O-bottle necks I think of making a symlink from pg_xlog to another
> physical disk.
> This is a modification inside the cluster dir. What kind of idea is that?
> bad one?
That's exactly the recommended way to put xlog on a separate disk.
Don't forget to shut down the postmaster while moving xlog around ;-)
regards, tom lane
Go for it, it's suggested: http://www.postgresql.org/docs/8.0/interactive/wal-internals.html Jason Minion IT Developer Sigler Printing & Publishing 413 Northwestern Ave Ames, IA 50010 515-232-6997 jason.minion@sigler.com -----Original Message----- From: pgsql-admin-owner@postgresql.org [mailto:pgsql-admin-owner@postgresql.org]On Behalf Of KÖPFERL Robert Sent: Friday, June 24, 2005 8:18 AM To: [ADMIN] Subject: [ADMIN] symlinking pg_xlog Hi, due to I/O-bottle necks I think of making a symlink from pg_xlog to another physical disk. This is a modification inside the cluster dir. What kind of idea is that? bad one? ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to majordomo@postgresql.org)
Last week I was testing PG under different RAID configurations and I moved pg_xlog to other drives and set up the symlink in the data directory (pg_xlog -> /home/test/pg-log). PG worked fine and there were no problems Tim ---------------------- Timothy Shenton Lycos, Inc. (781) 370-2876 |---------+--------------------------------> | | Michael Fuhr | | | <mike@fuhr.org> | | | Sent by: | | | pgsql-admin-owner@pos| | | tgresql.org | | | | | | | | | 06/24/2005 09:40 AM | | | | |---------+--------------------------------> >----------------------------------------------------------------------------------------------------------| | | | To: KÖPFERL Robert <robert.koepferl@sonorys.at> | | cc: "[ADMIN]" <pgsql-admin@postgresql.org> | | Subject: Re: [ADMIN] symlinking pg_xlog | >----------------------------------------------------------------------------------------------------------| On Fri, Jun 24, 2005 at 03:18:12PM +0200, KÖPFERL Robert wrote: > > due to I/O-bottle necks I think of making a symlink from pg_xlog to another > physical disk. > This is a modification inside the cluster dir. What kind of idea is that? > bad one? See the "Write-Ahead Logging (WAL)" chapter in the documentation: http://www.postgresql.org/docs/8.0/static/wal-internals.html "It is of advantage if the log is located on another disk than the main database files. This may be achieved by moving the directory pg_xlog to another location (while the server is shut down, of course) and creating a symbolic link from the original location in the main data directory to the new location." Several third-party performance-tuning documents make the same recommendation. -- Michael Fuhr http://www.fuhr.org/~mfuhr/ ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to majordomo@postgresql.org)
Thanks to all of you. I actually read the chapter but I just remembered to not touch pg's own area pg_* So ... I'll go for it |-----Original Message----- |From: Tom Lane [mailto:tgl@sss.pgh.pa.us] |Sent: Freitag, 24. Juni 2005 15:50 |To: KÖPFERL Robert |Cc: [ADMIN] |Subject: Re: [ADMIN] symlinking pg_xlog | | |=?iso-8859-1?Q?K=D6PFERL_Robert?= <robert.koepferl@sonorys.at> writes: |> due to I/O-bottle necks I think of making a symlink from |pg_xlog to another |> physical disk. |> This is a modification inside the cluster dir. What kind of |idea is that? |> bad one? | |That's exactly the recommended way to put xlog on a separate disk. | |Don't forget to shut down the postmaster while moving xlog around ;-) | | regards, tom lane |