I'm wondering why there is the recommendation to use "forcedirectio" on the ,mount options when it seems, at least on solaris, that filesystemio_options=directio is sufficient for using direct I/O? - Kyle http://dboptimizer.com On Mon, Apr 18, 2011 at 5:58 PM, kyle Hailey <kylelf@xxxxxxxxx> wrote: > > Testing on Solaris, I got direct I/O if either NFS mount was set > forcedirectio or Oracle had the parameter filesystemio_options=directio > > The only case I got unix files system caching was when the mount was done > without forcedirectio and filesystemio_options were either none or asynch. > > - Kyle > http://dboptimizer.com > > PS used dtrace on solaris to watch the file system access to see whether > the query was going to disk or not and watching the number of physical reads > with autotrace in sqlplus. The query was definitely doing the same physical > reads in all cases and in all cases the disks were accessed except when the > NFS mount was done without forcedirectio and filesystemio_options were > either none or asynch. Query was doing > 87129 consistent reads > 77951 physical reads > Of course the response time of the query was a good indicator. The second > execution of the query with Unix caching was about 5 seconds, with direct > I/O and 32K resize/wsize on the NFS mount it was 60 seconds and with 1M > rsize/wsize on the NFS mounts it was 30 seconds. (Looks like the rsize/wsize > can have a big impact ) > For this table, when cached in the buffer cache, it too 2 seconds, ie no > physical reads. > > > > > On Fri, Feb 11, 2011 at 3:11 PM, D'Hooge Freek <Freek.DHooge@xxxxxxxxx>wrote: > >> Gaja, >> X-archive-position: 34399 >> X-ecartis-version: Ecartis v1.0.0 >> Sender: oracle-l-bounce@xxxxxxxxxxxxx >> Errors-to: oracle-l-bounce@xxxxxxxxxxxxx >> X-original-sender: Freek.DHooge@xxxxxxxxx >> Precedence: normal >> Reply-To: Freek.DHooge@xxxxxxxxx >> List-help: <mailto:ecartis@xxxxxxxxxxxxx?Subject=help> >> List-unsubscribe: <oracle-l-request@xxxxxxxxxxxxx?Subject=unsubscribe> >> List-software: Ecartis version 1.0.0 >> List-Id: oracle-l <oracle-l.freelists.org> >> X-List-ID: oracle-l <oracle-l.freelists.org> >> List-subscribe: <oracle-l-request@xxxxxxxxxxxxx?Subject=subscribe> >> List-owner: <mailto:steve.adams@xxxxxxxxxxxx> >> List-post: <mailto:oracle-l@xxxxxxxxxxxxx> >> List-archive: <//www.freelists.org/archives/oracle-l> >> X-list: oracle-l >> >> This explains why the forcedirectio mount option is required with NFS on >> solaris. >> But I always thought that setting the filesystemio_options parameter to >> directIO or setall caused the processes to open the files with the O_DIRECT >> flag. If so, would this then not cause the file to be accessed with directio >> despite any setting on the filesystem? >> >> I'm working mainly on linux these days (either with nfs or asm), so not >> much chance in testing this. >> >> >> Regards, >> >> >> Freek D'Hooge >> Uptime >> Oracle Database Administrator >> email: freek.dhooge@xxxxxxxxx >> tel +32(0)3 451 23 82 >> http://www.uptime.be >> disclaimer: www.uptime.be/disclaimer >> --- >> From: Gaja Krishna Vaidyanatha [mailto:gajav@xxxxxxxxx] >> Sent: vrijdag 11 februari 2011 22:47 >> To: D'Hooge Freek >> Cc: Oracle-L List >> Subject: Re: How much RAM is to much >> >> Hi Freek, >> >> What you said is true for filesystems that do NOT allow "direct I/O" mount >> options in their respective mount commands. But for those filesystems that >> do (i.e. vxfs, jfs etc) support the relevant direct I/O mount options, the >> direct I/O mount option has always (in my experience) been required in >> addition to setting filesystemio_options to SETALL. Setting just the >> filesystemio_options in the init.ora (in those cases) did not create the >> desired result. >> >> If you have observed the "lack of the mount option" in recent times on >> those filesystems where direct I/O mount options ARE supported (i.e. vxfs, >> jfs etc), please advise. There is always something to learn new each day :) >> >> Cheers, >> >> Gaja >> >> Gaja Krishna Vaidyanatha, >> Founder/Principal, DBPerfMan LLC >> http://www.dbperfman.com >> Phone - 001-(650)-743-6060 >> Co-author:Oracle Insights:Tales of the Oak Table - >> http://www.apress.com/book/bookDisplay.html?bID=314 >> Co-author:Oracle Performance Tuning 101 - >> http://www.amazon.com/gp/reader/0072131454/ref=sib_dp_pt/102-6130796-4625766 >> -- >> //www.freelists.org/webpage/oracle-l >> >> >> >