Block vs. RAW
I'm setting up 12.10 on RHEL 6.7. Disks are on a SAN box. I'm using block devices and performance seems to be OK. Then I was thinking about using RAW (character devices) instead. Then I found this: https://access.redhat.com/solutions/183943?tour=6 <quote> Root Cause Raw device service is deprecated as of Red Hat Enterprise Linux 6.0. However, it is possible to bind the raw device by /etc/udev/rules.d/60-raw.rules. As of the Red Hat Enterprise Linux 6.0 release, the mode, uid|gid parameters have been deprecated. </quote> Deprecated. Should I stick to the block devices or would you recommend going through some hassle and use raw instead? Will the advantages outweigh the disadvantages? Thanks in advance, -Snorri
Snorri: Either use RAW or files in an EXT2 filesystem (or EXT3 or EXT4 with journaling disabled - EXT4 with journaling enabled is not safe) NOT block devices. Block devices have to be opened o_sync by the database engine to get safe writes and this is slow. If you use RAW it's not an issue. If you use filesystem files for Informix chunks and enable the DIRECT_IO parameter in your ONCONFIG file the engine can open the filesystem chunks using the o_direct flag which is MUCH faster. BLOCK or cooked devices are about 10% slower than RAW devices. Filesystem chunks without DIRECT_IO enabled are about 25% slower than RAW but with DIRECT_IO enabled they are only about 5% slower than raw. Art Art S. Kagel, President and Principal Consultant ASK Database Management www.askdbmgt.com Blog: http://informix-myview.blogspot.com/ Disclaimer: Please keep in mind that my own opinions are my own opinions and do not reflect on the IIUG, nor any other organization with which I am associated either explicitly, implicitly, or by inference. Neither do those opinions reflect those of other individuals affiliated with any entity with which I am affiliated nor those of the entities themselves. On Thu, Dec 3, 2015 at 9:38 AM, SNORRI BERGMANN <snorri@init.is> wrote: > I'm setting up 12.10 on RHEL 6.7. Disks are on a SAN box. I'm using block > devices and performance seems to be OK. Then I was thinking about using RAW > (character devices) instead. Then I found this: > > https://access.redhat.com/solutions/183943?tour=6 > > <quote> > > Root Cause > > Raw device service is deprecated as of Red Hat Enterprise Linux 6.0. > However, > it is possible to bind the raw device by /etc/udev/rules.d/60-raw.rules. > As of the Red Hat Enterprise Linux 6.0 release, the mode, uid|gid > parameters > have been deprecated. > > </quote> > > Deprecated. Should I stick to the block devices or would you recommend > going > through some hassle and use raw instead? Will the advantages outweigh the > disadvantages? > > Thanks in advance, > -Snorri > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --001a113fe84e552e390525ffe3ed
Thanks Art. Unfortunately, I can't use a filesystem (except maybe gvfs) because this will be an SDS instance. EXTx filesystems are not safe to be mounted by two servers at the same time (or so I'm being told). I think I will try to config this using RAW and see if I see any differences. Thanks, -Snorri
Got it. Yeah, I wouldn't try to use a virtual FS like gvfs for chunks either. Art Art S. Kagel, President and Principal Consultant ASK Database Management www.askdbmgt.com Blog: http://informix-myview.blogspot.com/ Disclaimer: Please keep in mind that my own opinions are my own opinions and do not reflect on the IIUG, nor any other organization with which I am associated either explicitly, implicitly, or by inference. Neither do those opinions reflect those of other individuals affiliated with any entity with which I am affiliated nor those of the entities themselves. On Thu, Dec 3, 2015 at 10:32 AM, SNORRI BERGMANN <snorri@init.is> wrote: > Thanks Art. > > Unfortunately, I can't use a filesystem (except maybe gvfs) because this > will > be an SDS instance. EXTx filesystems are not safe to be mounted by two > servers > at the same time (or so I'm being told). > > I think I will try to config this using RAW and see if I see any > differences. > > Thanks, > -Snorri > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --001a113fe84e28bfba0526002c69