Raw or cook devices?
A user planning IDS 11.7 on SUSE Linux (later virtualised) asked whether to use raw or cooked chunks. Replies split: one advised raw for best performance, another said they had to move to cooked files on their SUSE release, while others noted cooked chunks with DIRECT_IO perform comparably and that LVM or udev rules (e.g. /etc/udev/rules.d entries mapping devices with informix ownership) can provide raw devices; the I/O scheduler choice was also suggested as a tuning point. Art Kagel said the raw-vs-cooked difference is usually small and the bigger issues are avoiding RAID5 (data-safety and write-penalty concerns, citing baarf.com) and journaled filesystems, recommending RAID10 (RAID1 for small LUNs like logs/temp) and EXT2/EXT3 with journaling disabled. No single definitive answer on raw vs cooked was recorded.
Auto-generated by DrWatson from the posts below — may be imperfect; read the full thread.
I'm planing to install an ids 11.7 on suse linux, after that I like to make this linux into a virtual machine. What recomend to use raw or cooked devices? Thanks in advance. Enviado desde mi iPhone
Hi Jorge Always raw devices for best performance. Regards Rubén El mié, 11-02-2015 a las 19:31 -0500, Jorge Valenzuela escribió: > I'm planing to install an ids 11.7 on suse linux, after that I like to make > this linux into a virtual machine. > > What recomend to use raw or cooked devices? > > Thanks in advance. > > Enviado desde mi iPhone > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.
When we went to Suse 11.7 we had to move to cooked files. I don't think Suse 11.7 supports raw devices. Thank you, Jim Goldrick (573) 979-9079 jgoldrick@judsonu.edu Reminder: Judson University IT will never ask for your password or other personal information over email. Judson University | Elgin, IL 60123 | JudsonU.edu Committed to the Student, Spiritual Development and Excellence -----Original Message----- From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of Rubén Dután Sent: Wednesday, February 11, 2015 7:07 PM To: ids@iiug.org Subject: Re: Raw or cook devices? [34626] Hi Jorge Always raw devices for best performance. Regards Rubén El mié, 11-02-2015 a las 19:31 -0500, Jorge Valenzuela escribió: > I'm planing to install an ids 11.7 on suse linux, after that I like to > make this linux into a virtual machine. > > What recomend to use raw or cooked devices? > > Thanks in advance. > > Enviado desde mi iPhone > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. ******************************************************************************* Forum Note: Use "Reply" to post a response in the discussion forum.
LVM can be used... But with DIRECT_IO the performance is probably enough with cooked devices Regards On Thu, Feb 12, 2015 at 1:20 AM, Goldrick, Jim <jgoldrick@judsonu.edu> wrote: > When we went to Suse 11.7 we had to move to cooked files. I don't think > Suse > 11.7 supports raw devices. > > Thank you, > Jim Goldrick > (573) 979-9079 > jgoldrick@judsonu.edu > Reminder: Judson University IT will never ask for your password or other > personal information over email. > > Judson University | Elgin, IL 60123 | JudsonU.edu > Committed to the Student, Spiritual Development and Excellence > > -----Original Message----- > From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of > Rubén > Dután > Sent: Wednesday, February 11, 2015 7:07 PM > To: ids@iiug.org > Subject: Re: Raw or cook devices? [34626] > > Hi Jorge > > Always raw devices for best performance. > Regards > Rubén > El mié, 11-02-2015 a las 19:31 -0500, Jorge Valenzuela escribió: > > I'm planing to install an ids 11.7 on suse linux, after that I like to > > make this linux into a virtual machine. > > > > What recomend to use raw or cooked devices? > > > > Thanks in advance. > > > > Enviado desde mi iPhone > > > > > > > > > ******************************************************************************* > > Forum Note: Use "Reply" to post a response in the discussion forum. > > > > > > -- > This message has been scanned for viruses and dangerous content by > MailScanner, and is believed to be clean. > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > -- Fernando Nunes Portugal http://informix-technology.blogspot.com My email works... but I don't check it frequently... --001a11c317fc4ffd8c050ed9fc62
My experience is that some linux systems perform best with raw others with cooked and direct_io. I haven't been able to nail down why. Hiwever, the difference is usuallt small. Most important? No RAID5 and no journaled filesystems. So EXT2 or EXT3 with the journal disabled (same except that you can expand an EXT3 fileststem while it is mounted while EXT2 has to be unmounted to expand it). Art On Feb 11, 2015 7:32 PM, "Jorge Valenzuela" <jorgervt@gmail.com> wrote: > I'm planing to install an ids 11.7 on suse linux, after that I like to make > this linux into a virtual machine. > > What recomend to use raw or cooked devices? > > Thanks in advance. > > Enviado desde mi iPhone > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --001a11c36986adff24050eda4b33
Thanks. I'm planing use RAID 5. Raid 5 is not recomendable to use ? Enviado desde mi iPhone > El 11/02/2015, a las 17:47, Art Kagel <art.kagel@gmail.com> escribió: > > My experience is that some linux systems perform best with raw others with > cooked and direct_io. I haven't been able to nail down why. Hiwever, the > difference is usuallt small. Most important? No RAID5 and no journaled > filesystems. So EXT2 or EXT3 with the journal disabled (same except that > you can expand an EXT3 fileststem while it is mounted while EXT2 has to be > unmounted to expand it). > > Art >> On Feb 11, 2015 7:32 PM, "Jorge Valenzuela" <jorgervt@gmail.com> wrote: >> >> I'm planing to install an ids 11.7 on suse linux, after that I like to make >> this linux into a virtual machine. >> >> What recomend to use raw or cooked devices? >> >> Thanks in advance. >> >> Enviado desde mi iPhone > ******************************************************************************* >> Forum Note: Use "Reply" to post a response in the discussion forum. > > --001a11c36986adff24050eda4b33 > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. >
Jorge: RAID5 is not safe for your data. Period. If that's not enough, RAID5 write performance is 50% of the equivalent RAID10 array. Here's a link to a web site that has documentation about the problems with RAID5 including a paper I wrote and others be well known authors: www.baarf.com 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 Wed, Feb 11, 2015 at 9:27 PM, Jorge Valenzuela <jorgervt@gmail.com> wrote: > Thanks. I'm planing use RAID 5. Raid 5 is not recomendable to use ? > > Enviado desde mi iPhone > > > El 11/02/2015, a las 17:47, Art Kagel <art.kagel@gmail.com> escribió: > > > > My experience is that some linux systems perform best with raw others > with > > cooked and direct_io. I haven't been able to nail down why. Hiwever, the > > difference is usuallt small. Most important? No RAID5 and no journaled > > filesystems. So EXT2 or EXT3 with the journal disabled (same except that > > you can expand an EXT3 fileststem while it is mounted while EXT2 has to > be > > unmounted to expand it). > > > > Art > >> On Feb 11, 2015 7:32 PM, "Jorge Valenzuela" <jorgervt@gmail.com> wrote: > >> > >> I'm planing to install an ids 11.7 on suse linux, after that I like to > make > >> this linux into a virtual machine. > >> > >> What recomend to use raw or cooked devices? > >> > >> Thanks in advance. > >> > >> Enviado desde mi iPhone > > > > ******************************************************************************* > >> Forum Note: Use "Reply" to post a response in the discussion forum. > > > > --001a11c36986adff24050eda4b33 > > > > > > > > ******************************************************************************* > > Forum Note: Use "Reply" to post a response in the discussion forum. > > > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --001a1134163cb34ae7050edbdee5
I read the article, vis ery interesting. So your recomendation is raid 10 ? Enviado desde mi iPhone > El 11/02/2015, a las 19:39, Art Kagel <art.kagel@gmail.com> escribió: > > Jorge: > > RAID5 is not safe for your data. Period. If that's not enough, RAID5 > write performance is 50% of the equivalent RAID10 array. > > Here's a link to a web site that has documentation about the problems with > RAID5 including a paper I wrote and others be well known authors: > > www.baarf.com > > 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 Wed, Feb 11, 2015 at 9:27 PM, Jorge Valenzuela <jorgervt@gmail.com> > wrote: > >> Thanks. I'm planing use RAID 5. Raid 5 is not recomendable to use ? >> >> Enviado desde mi iPhone >> >>> El 11/02/2015, a las 17:47, Art Kagel <art.kagel@gmail.com> escribió: >>> >>> My experience is that some linux systems perform best with raw others >> with >>> cooked and direct_io. I haven't been able to nail down why. Hiwever, the >>> difference is usuallt small. Most important? No RAID5 and no journaled >>> filesystems. So EXT2 or EXT3 with the journal disabled (same except that >>> you can expand an EXT3 fileststem while it is mounted while EXT2 has to >> be >>> unmounted to expand it). >>> >>> Art >>>> On Feb 11, 2015 7:32 PM, "Jorge Valenzuela" <jorgervt@gmail.com> wrote: >>>> >>>> I'm planing to install an ids 11.7 on suse linux, after that I like to >> make >>>> this linux into a virtual machine. >>>> >>>> What recomend to use raw or cooked devices? >>>> >>>> Thanks in advance. >>>> >>>> Enviado desde mi iPhone > ******************************************************************************* >>>> Forum Note: Use "Reply" to post a response in the discussion forum. >>> >>> --001a11c36986adff24050eda4b33 > ******************************************************************************* >>> Forum Note: Use "Reply" to post a response in the discussion forum. > ******************************************************************************* >> Forum Note: Use "Reply" to post a response in the discussion forum. > > --001a1134163cb34ae7050edbdee5 > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. >
Yes. RAID10 in general, RAID1 for smaller luns if you need to isolate IOs for some smaller chunks like logical or physical logs or temp dbspaces. 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, Feb 12, 2015 at 9:46 AM, Jorge Valenzuela <jorgervt@gmail.com> wrote: > I read the article, vis ery interesting. So your recomendation is raid 10 ? > > Enviado desde mi iPhone > > > El 11/02/2015, a las 19:39, Art Kagel <art.kagel@gmail.com> escribió: > > > > Jorge: > > > > RAID5 is not safe for your data. Period. If that's not enough, RAID5 > > write performance is 50% of the equivalent RAID10 array. > > > > Here's a link to a web site that has documentation about the problems > with > > RAID5 including a paper I wrote and others be well known authors: > > > > www.baarf.com > > > > 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 Wed, Feb 11, 2015 at 9:27 PM, Jorge Valenzuela <jorgervt@gmail.com> > > wrote: > > > >> Thanks. I'm planing use RAID 5. Raid 5 is not recomendable to use ? > >> > >> Enviado desde mi iPhone > >> > >>> El 11/02/2015, a las 17:47, Art Kagel <art.kagel@gmail.com> escribió: > >>> > >>> My experience is that some linux systems perform best with raw others > >> with > >>> cooked and direct_io. I haven't been able to nail down why. Hiwever, > the > >>> difference is usuallt small. Most important? No RAID5 and no journaled > >>> filesystems. So EXT2 or EXT3 with the journal disabled (same except > that > >>> you can expand an EXT3 fileststem while it is mounted while EXT2 has to > >> be > >>> unmounted to expand it). > >>> > >>> Art > >>>> On Feb 11, 2015 7:32 PM, "Jorge Valenzuela" <jorgervt@gmail.com> > wrote: > >>>> > >>>> I'm planing to install an ids 11.7 on suse linux, after that I like to > >> make > >>>> this linux into a virtual machine. > >>>> > >>>> What recomend to use raw or cooked devices? > >>>> > >>>> Thanks in advance. > >>>> > >>>> Enviado desde mi iPhone > > > > ******************************************************************************* > >>>> Forum Note: Use "Reply" to post a response in the discussion forum. > >>> > >>> --001a11c36986adff24050eda4b33 > > > > ******************************************************************************* > >>> Forum Note: Use "Reply" to post a response in the discussion forum. > > > > ******************************************************************************* > >> Forum Note: Use "Reply" to post a response in the discussion forum. > > > > --001a1134163cb34ae7050edbdee5 > > > > > > > > ******************************************************************************* > > Forum Note: Use "Reply" to post a response in the discussion forum. > > > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --001a11c32cf098fee1050ee54898
FYI, if you go onto the IIUG Site's members area, Conference Downloads, you can download a presentation I did at the IIUG Conference in 2012 about storage in general. It includes reference to some recent research that backs up my contention that RAID5 is evil. The file is: B09_Kagel_Doing_Strage_Better.pdf 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, Feb 12, 2015 at 9:52 AM, Art Kagel <art.kagel@gmail.com> wrote: > Yes. RAID10 in general, RAID1 for smaller luns if you need to isolate IOs > for some smaller chunks like logical or physical logs or temp dbspaces. > > 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, Feb 12, 2015 at 9:46 AM, Jorge Valenzuela <jorgervt@gmail.com> > wrote: > >> I read the article, vis ery interesting. So your recomendation is raid 10 >> ? >> >> Enviado desde mi iPhone >> >> > El 11/02/2015, a las 19:39, Art Kagel <art.kagel@gmail.com> escribió: >> > >> > Jorge: >> > >> > RAID5 is not safe for your data. Period. If that's not enough, RAID5 >> > write performance is 50% of the equivalent RAID10 array. >> > >> > Here's a link to a web site that has documentation about the problems >> with >> > RAID5 including a paper I wrote and others be well known authors: >> > >> > www.baarf.com >> > >> > 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 Wed, Feb 11, 2015 at 9:27 PM, Jorge Valenzuela <jorgervt@gmail.com> >> > wrote: >> > >> >> Thanks. I'm planing use RAID 5. Raid 5 is not recomendable to use ? >> >> >> >> Enviado desde mi iPhone >> >> >> >>> El 11/02/2015, a las 17:47, Art Kagel <art.kagel@gmail.com> escribió: >> >>> >> >>> My experience is that some linux systems perform best with raw others >> >> with >> >>> cooked and direct_io. I haven't been able to nail down why. Hiwever, >> the >> >>> difference is usuallt small. Most important? No RAID5 and no journaled >> >>> filesystems. So EXT2 or EXT3 with the journal disabled (same except >> that >> >>> you can expand an EXT3 fileststem while it is mounted while EXT2 has >> to >> >> be >> >>> unmounted to expand it). >> >>> >> >>> Art >> >>>> On Feb 11, 2015 7:32 PM, "Jorge Valenzuela" <jorgervt@gmail.com> >> wrote: >> >>>> >> >>>> I'm planing to install an ids 11.7 on suse linux, after that I like >> to >> >> make >> >>>> this linux into a virtual machine. >> >>>> >> >>>> What recomend to use raw or cooked devices? >> >>>> >> >>>> Thanks in advance. >> >>>> >> >>>> Enviado desde mi iPhone >> > >> >> ******************************************************************************* >> >>>> Forum Note: Use "Reply" to post a response in the discussion forum. >> >>> >> >>> --001a11c36986adff24050eda4b33 >> > >> >> ******************************************************************************* >> >>> Forum Note: Use "Reply" to post a response in the discussion forum. >> > >> >> ******************************************************************************* >> >> Forum Note: Use "Reply" to post a response in the discussion forum. >> > >> > --001a1134163cb34ae7050edbdee5 >> > >> > >> > >> >> ******************************************************************************* >> > Forum Note: Use "Reply" to post a response in the discussion forum. >> > >> >> >> >> ******************************************************************************* >> Forum Note: Use "Reply" to post a response in the discussion forum. >> >> > --001a11c3486410494d050ee559b2
Is the write performance of the actual disks a determining factor any more on a modern SAN? Most stuff is either purely solid state now or pushes all writes through a battery-backed solid state disks, which don't necessarily have the same RAID set up as the underlying spinning disks.
When you say it doesn't support raw devices, do you actually mean it doesn't support raw devices in the form of /etc/raw/rawX ? I don't use SUSE but I am pretty sure that on all modern Linux distributions you can use udev to configure raw devices. An example on RHEL which might work on SUSE: File '/etc/udev/rules.d/99-informix-rawdevices.rules' with contents: KERNEL=="sdb", NAME="informix/data_01", OWNER="informix", GROUP="informix", MODE="0660", ATTR{queue/scheduler}="deadline" KERNEL=="sdc", NAME="informix/logs_01", OWNER="informix", GROUP="informix", MODE="0660", ATTR{queue/scheduler}="deadline" Restart udev and you will have block-special devices with the correct privileges: /dev/informix/data_01 /dev/informix/logs_01 I think you can use an LVM underneath instead of whole disks. I have mentioned this before but no-one seemed interested so I'll mention it again... :) In modern Linux you have a choice of schedulers for how the kernel services I/O requests. Some useful comments here: http://stackoverflow.com/questions/1009577/selecting-a-linux-i-o-scheduler The default scheduler is the fair queuing scheduler which may not be the best for a database.
In the richer parts of the world then that is certainly true, but it is not the case elsewhere. There you still have all the old issues Cheers Paul > -----Original Message----- > From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of > BENJAMIN THOMPSON > Sent: Thursday, February 12, 2015 9:11 AM > To: ids@iiug.org > Subject: Re: Raw or cook devices? [34640] > > Is the write performance of the actual disks a determining factor any more > on > a modern SAN? Most stuff is either purely solid state now or pushes all > writes > through a battery-backed solid state disks, which don't necessarily have the > same RAID set up as the underlying spinning disks. > > > ********************************************************** > ********************* > Forum Note: Use "Reply" to post a response in the discussion forum.
The performance issues with RAID5 are sevondary to tge data ssfety issues. That said, unless your SAN has unlimited cache, it has to flush writes sometime and at that point yes the RAID5 write penalty will indeed have an effect. Art On Feb 12, 2015 10:13 AM, "BENJAMIN THOMPSON" <benjamin.thompson@bskyb.com> wrote: > Is the write performance of the actual disks a determining factor any more > on > a modern SAN? Most stuff is either purely solid state now or pushes all > writes > through a battery-backed solid state disks, which don't necessarily have > the > same RAID set up as the underlying spinning disks. > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --001a11c3c51625c7cd050ee699ea
A good story about RAID 5 ... I remember landing onsite at a client for "all of a sudden performance issues" on IDS. Did all the typical research on what happened over the weekend - any new crons, upd stats failed, new apps released, rogue sqls and all the typical engine health check items. Nothing turning up. Was about to look at I/O but got called onto a conf call. The SA said very casually "no other changes this weekend other than moving the disks to RAID 5." He hadn't told anyone, let alone understood the potential impact of what isn't a "flip of a switch" change. Was very bizarre. Eventually we "undid" what he did and of course, performance returned to normal. Mark Scranton The Mark Scranton Group "All Informix ... all the time." www.markscranton.com mark@markscranton.com
Beautiful! Or Ugly. Depends on your attitude I guess. Mind if I share that (attributed or not - up to you)? 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 Wed, Feb 18, 2015 at 12:30 PM, MARK SCRANTON <mark@markscranton.com> wrote: > A good story about RAID 5 ... I remember landing onsite at a client for > "all > of a sudden performance issues" on IDS. Did all the typical research on > what > happened over the weekend - any new crons, upd stats failed, new apps > released, rogue sqls and all the typical engine health check items. Nothing > turning up. Was about to look at I/O but got called onto a conf call. The > SA > said very casually "no other changes this weekend other than moving the > disks > to RAID 5." He hadn't told anyone, let alone understood the potential > impact > of what isn't a "flip of a switch" change. Was very bizarre. Eventually we > "undid" what he did and of course, performance returned to normal. > > Mark Scranton > The Mark Scranton Group > "All Informix ... all the time." > www.markscranton.com > mark@markscranton.com > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --001a11c34864631cdf050f604198