Re: ext3

You may also want to test data=journal for ext3. Most of the time, this
is slower but for databases with logging and mail servers, it can be faster.

Mage wrote:
> Hello,
>
> Gabor Szima asked us to translate the letter below.
>
> "I read that ext3 writeback mode is recommended for PostgreSQL. I made
> some tests.
>
> data=ordered data=writeback
> ----------------------------------------------------------------------
> restoredb: 2m16.790s 1m42.367s
> UPDATE <tbl1> (17krows): 9.289s 7.147s
> UPDATE <tbl1> (17krows) (2.): 10.480s 3.778s
> VACUUM ANALYZE <tbl1>: 9.364s 0.986s !
> VACUUM FULL <tbl1>: 16.071s 2.575s
> REINDEX TABLE <tbl1>: 3.815s 1.886s
> ----------------------------------------------------------------------
>
> It's seductive.
> However I made some crash-tests too. Updated 4 tables simultaneously and
> recurring for 10 to 120s, then powered off the machine (without the
> reset button. i just pulled out the cable).
>
> SEQ RECOVERY-WARNINGS VACUUM
> -------------------------------
> 01: 1650 OK (WARNING: invalid page header in
> block 769 of relation "18800"; zeroing out page)
> 02: 3 FATAL (ERROR: could not access status of
> transaction 37814272)
> ------------------------------- (DETAIL: could not open file
> "/data/pgdata/pg_clog/0024": No such file or directory)
>
> I have stopped my tests at this point because this is not for production
> use. The database was corrupted.
>
>
> With ordered mode I got this:
>
> ext3-noatime,data=ordered:
>
> SEQ RECOVERY-WARNINGS VACUUM
> ------------------------------
> 01: 0 OK
> 02: 0 OK
> 03: 0 OK
> 04: 0 W,OK (relation "<tbl>" page 398 is
> uninitialized --- fixing)
> 05: 0 OK
> 06: 0 OK
> 07: 0 W,OK (relation "<tbl>" page 911 is
> uninitialized --- fixing)
> 08: 0 OK
> 09: 0 OK
> 10: 0 OK
> ------------------------------
>
> I think that writeback mode first records the data then the inode, and
> the ordered mode does it in reverse order. I also mean that postgres
> log requires the inode recorded correctly, the data loss is handled by
> the WAL.
>
> AMD XP2000, 512MB RAM, PostgreSQL 7.4.6 (i686), linux-2.4.28, gcc-3.3.5,
> Adaptec 29160, WD Enterprise 4360 (SCSI, SCA-80)