Carlos,
I agree with you. The performance degradation was very high on an
ext4 file system ( which has barrier enabled by default ). On the other
hand, I found no noticiable performance degradation on an ext3 file
system ( which has barrier disabled by default ).
Having barrier disabled on a server with an ext3 file system, does
FW=ON improve reliability or is it useless ?
Aldo Caruso
El 18/08/14 a las 16:27, 'Carlos H. Cantu' [email protected]
[firebird-support] escibió:
Usually, if you turn FW = ON on Linux, and your filesystem has barrier
enabled, it will affect performance of batch updates really badly.
You would either accept the performance degradation, or disable one of
them (FW or barrier).
Carlos
Firebird Performance in Detail - http://videos.firebirddevelopersday.com
www.firebirdnews.org - www.FireBase.com.br
ACacacfs> Hello,
ACacacfs> For reliability reasons, I decided to turn on forced writes
on a
ACacacfs> database running on Linux.
ACacacfs> After that I noticed that some massive updates ( 100K
records ) took
ACacacfs> nearly 5 minutes, whereas with async writes it used to take
10 seconds.
ACacacfs> One solution is, of course, disabling sync writes when doing
massive
ACacacfs> updates. Unfortunately not always massive updates are under
database
ACacacfs> admin control ( some end users actions can lead to massive
updates,
ACacacfs> indirectly, by means of triggers ).
ACacacfs> Another aproach I tested was augmenting page size from its
default
ACacacfs> value ( 4 KB ) to its maximum allowed value ( 16 KB ). The
speed was
ACacacfs> notably enhaced ( 1 minute for the update + 10 seconds for
the commit,
ACacacfs> but sometimes 2 seconds for the update and 40 seconds for
the commit).
ACacacfs> It should be pointed out that 4 KB was fine, taking into
account
ACacacfs> record size ( max. 300 bytes ) and index max depth ( always
< 3 ).
ACacacfs> Going one step further, I augmented cached pages from its
default (
ACacacfs> 2048 ) to 8192. Some small performance improvement was
observed, but not
ACacacfs> very significative. It shoud be noted also that, with a 16
KB page size,
ACacacfs> the database has 5700 pages on disk, so there are enough
cache pages to
ACacacfs> hold the entire database.
ACacacfs> Given this scenario my questions are the following:
ACacacfs> 1) Does it makes sense to activate forced writes on Linux ?
ACacacfs> 2) Is increasing the page size the right approach to improve
performance
ACacacfs> ? Which are the drawbacks of setting page size to 16K ?
ACacacfs> 3) The same question stands for cache pages: is it useful (
or has
ACacacfs> disadvantages ) to have so many cache pages as there are on
disk pages (
ACacacfs> provided there is enough RAM size ) ?
ACacacfs> Thanks in advance for any clue.
ACacacfs> Aldo
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