Chunk Size

Hello Group, Do you have a recommendation on what to set the raw chunk size? Currently we are using raw devices and are split into 2GB chunks. Our storage admins would prefer to give us larger chunk sizes for future disk allocation and want us to recommend a chunk size. Is there a recommendation on a good size to use considering that we are running informix as follows: Informix 11.70.FC7W2 Primary OLTP Envirnoment mixed with reporting Solaris 10 Currently using 440 2GB chunks across 11 DB Spaces. Any suggestions would be greatly appreciated. Thank You, --Dave --089e0158ace071e35c04eb288f8f

Very good question, not a very good answer.... but: -dbspaces are logic units... And considering it's what we "see" at SQL level, it depends on your data and usage - lots of small chunks vs few big chunks... We don't do split a chunk through several cleaners at checkpoint. So having just "one" chunk would be bad... But with your database size 2GB is really small... I usually go for 4 or 8GB... Also because typically only a few are "live" and the others tend to have historic data... (and I don't want the live ones very big). If you can split your data between "static" and "live" I wouldn't se a problem in going above that for "static" - It can also be a function of your feeling when you do an "onstat 'd" and get several pages of info... ;) Regards On Nov 14, 2013 8:02 PM, "Informix DBA" <in4mixdba@gmail.com> wrote: > Hello Group, > > Do you have a recommendation on what to set the raw chunk size? Currently > we are using raw devices and are split into 2GB chunks. Our storage admins > would prefer to give us larger chunk sizes for future disk allocation and > want us to recommend a chunk size. Is there a recommendation on a good > size to use considering that we are running informix as follows: > > Informix 11.70.FC7W2 > Primary OLTP Envirnoment mixed with reporting > Solaris 10 > Currently using 440 2GB chunks across 11 DB Spaces. > > Any suggestions would be greatly appreciated. > > Thank You, > > --Dave > > --089e0158ace071e35c04eb288f8f > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --bcaec54858f6d3af7304eb28d90f

OK, here are the trade offs: At checkpoint time Informix flushes dirty pages to disk with one cleaner thread per chunk (up to the number of configured cleaner threads of course). So, the more chunks the more parallelism at checkpoint time. On the other hand, fewer bigger chunks are definitely easier to manage from a hardware, adminstration, and DBA perspective, so you try to balance that. Figure out your maximum checkpoint IO volume, figure out how many DBspaces that will involve, calculate the maximum throughput of those VGs and divide. That's your fewest number of viable chunks. Art Art S. Kagel, Principal Consultant Advanced DataTools (www.advancedatatools.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 my employer, Advanced DataTools, 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, Nov 14, 2013 at 3:02 PM, Informix DBA <in4mixdba@gmail.com> wrote: > Hello Group, > > Do you have a recommendation on what to set the raw chunk size? Currently > we are using raw devices and are split into 2GB chunks. Our storage admins > would prefer to give us larger chunk sizes for future disk allocation and > want us to recommend a chunk size. Is there a recommendation on a good > size to use considering that we are running informix as follows: > > Informix 11.70.FC7W2 > Primary OLTP Envirnoment mixed with reporting > Solaris 10 > Currently using 440 2GB chunks across 11 DB Spaces. > > Any suggestions would be greatly appreciated. > > Thank You, > > --Dave > > --089e0158ace071e35c04eb288f8f > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --001a11c3c4fe080a7e04eb2908c5

Thank you Fernando and Art for the good information. Like many things you are correct that it needs to be a balance of various factors. I know Fernando you suggested 4 or 8gb. What other sizes are people typically using on their Informix OLTP systems? --Dave On Thu, Nov 14, 2013 at 3:36 PM, Art Kagel <art.kagel@gmail.com> wrote: > OK, here are the trade offs: At checkpoint time Informix flushes dirty > pages to disk with one cleaner thread per chunk (up to the number of > configured cleaner threads of course). So, the more chunks the more > parallelism at checkpoint time. On the other hand, fewer bigger chunks are > definitely easier to manage from a hardware, adminstration, and DBA > perspective, so you try to balance that. Figure out your maximum > checkpoint IO volume, figure out how many DBspaces that will involve, > calculate the maximum throughput of those VGs and divide. That's your > fewest number of viable chunks. > > Art > > Art S. Kagel, Principal Consultant > > Advanced DataTools (www.advancedatatools.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 my employer, Advanced DataTools, 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, Nov 14, 2013 at 3:02 PM, Informix DBA <in4mixdba@gmail.com> wrote: > > > Hello Group, > > > > Do you have a recommendation on what to set the raw chunk size? Currently > > we are using raw devices and are split into 2GB chunks. Our storage > admins > > would prefer to give us larger chunk sizes for future disk allocation and > > want us to recommend a chunk size. Is there a recommendation on a good > > size to use considering that we are running informix as follows: > > > > Informix 11.70.FC7W2 > > Primary OLTP Envirnoment mixed with reporting > > Solaris 10 > > Currently using 440 2GB chunks across 11 DB Spaces. > > > > Any suggestions would be greatly appreciated. > > > > Thank You, > > > > --Dave > > > > --089e0158ace071e35c04eb288f8f > > > > > > > > > > ******************************************************************************* > > Forum Note: Use "Reply" to post a response in the discussion forum. > > > > > > --001a11c3c4fe080a7e04eb2908c5 > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --089e0116136a82522d04eb2a562d

Hi, as Art stated, it depends on different factors. For a OLTP System, we use typically 20GB chunks, placed on SAS 15k disks with raid 10. For long lasting data, which is not modified frequently (like archives from documents etc., we have to keep 10 years), we use 50-100GB chunks (50GB for the tables, 100 GB for the SBLOB content). This is a separate instance with reduced buffer settings, having its own set of disks (SATA, raid 1, here all access is index based via a surrogate key, so no table scans, mostly insert and access through primary key, always the last added chunk has activity, the older ones rarely). Also, page size depends. we have some huge tables (in terms of row size), which are placed in 8kb dbspaces. Working mostly with IDS11.70FC5 on Linux. Last but not least, the blocksize of the raid array might be important. If you choose e.g. 128k, you might run good for a system, which has to manage periodic sequential inserts in a huge table (or stores photo or video data, the you could choose even bigger sizes). If you have OLTP (=random access), choose a blocksize closer to the page size (like 16k). You can see, the parameters vary depending on your needs. Marcus Haarmann ----- Ursprüngliche Mail ----- Von: "Informix DBA" <in4mixdba@gmail.com> An: ids@iiug.org Gesendet: Donnerstag, 14. November 2013 23:09:45 Betreff: Re: Chunk Size [31950] Thank you Fernando and Art for the good information. Like many things you are correct that it needs to be a balance of various factors. I know Fernando you suggested 4 or 8gb. What other sizes are people typically using on their Informix OLTP systems? --Dave On Thu, Nov 14, 2013 at 3:36 PM, Art Kagel <art.kagel@gmail.com> wrote: > OK, here are the trade offs: At checkpoint time Informix flushes dirty > pages to disk with one cleaner thread per chunk (up to the number of > configured cleaner threads of course). So, the more chunks the more > parallelism at checkpoint time. On the other hand, fewer bigger chunks are > definitely easier to manage from a hardware, adminstration, and DBA > perspective, so you try to balance that. Figure out your maximum > checkpoint IO volume, figure out how many DBspaces that will involve, > calculate the maximum throughput of those VGs and divide. That's your > fewest number of viable chunks. > > Art > > Art S. Kagel, Principal Consultant > > Advanced DataTools (www.advancedatatools.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 my employer, Advanced DataTools, 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, Nov 14, 2013 at 3:02 PM, Informix DBA <in4mixdba@gmail.com> wrote: > > > Hello Group, > > > > Do you have a recommendation on what to set the raw chunk size? Currently > > we are using raw devices and are split into 2GB chunks. Our storage > admins > > would prefer to give us larger chunk sizes for future disk allocation and > > want us to recommend a chunk size. Is there a recommendation on a good > > size to use considering that we are running informix as follows: > > > > Informix 11.70.FC7W2 > > Primary OLTP Envirnoment mixed with reporting > > Solaris 10 > > Currently using 440 2GB chunks across 11 DB Spaces. > > > > Any suggestions would be greatly appreciated. > > > > Thank You, > > > > --Dave > > > > --089e0158ace071e35c04eb288f8f > > > > > > > > > > ******************************************************************************* > > Forum Note: Use "Reply" to post a response in the discussion forum. > > > > > > --001a11c3c4fe080a7e04eb2908c5 > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --089e0116136a82522d04eb2a562d ******************************************************************************* Forum Note: Use "Reply" to post a response in the discussion forum.

Dave I have an instance of around 700 Gb with about 70 chunks of 4Gb and 8Gb. The mixture comes from the size of tables or whether the space is holding data or indexes. Regardless of the size of the database I would always aim (at least for 'normal' data) to have between 15 and 25 dbspaces with no more than 5 or 6 chunks per space and chunks of 4 and 8 Gb. IDS 9 was marvellous in that it allowed chunks larger than 2 Gb and significantly reduced admin overheads, take advantage of this feature. Keith On 14 November 2013 22:09, Informix DBA <in4mixdba@gmail.com> wrote: > Thank you Fernando and Art for the good information. Like many things you > are correct that it needs to be a balance of various factors. > > I know Fernando you suggested 4 or 8gb. What other sizes are people > typically using on their Informix OLTP systems? > > --Dave > > On Thu, Nov 14, 2013 at 3:36 PM, Art Kagel <art.kagel@gmail.com> wrote: > > > OK, here are the trade offs: At checkpoint time Informix flushes dirty > > pages to disk with one cleaner thread per chunk (up to the number of > > configured cleaner threads of course). So, the more chunks the more > > parallelism at checkpoint time. On the other hand, fewer bigger chunks > are > > definitely easier to manage from a hardware, adminstration, and DBA > > perspective, so you try to balance that. Figure out your maximum > > checkpoint IO volume, figure out how many DBspaces that will involve, > > calculate the maximum throughput of those VGs and divide. That's your > > fewest number of viable chunks. > > > > Art > > > > Art S. Kagel, Principal Consultant > > > > Advanced DataTools (www.advancedatatools.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 my employer, Advanced DataTools, 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, Nov 14, 2013 at 3:02 PM, Informix DBA <in4mixdba@gmail.com> > wrote: > > > > > Hello Group, > > > > > > Do you have a recommendation on what to set the raw chunk size? > Currently > > > we are using raw devices and are split into 2GB chunks. Our storage > > admins > > > would prefer to give us larger chunk sizes for future disk allocation > and > > > want us to recommend a chunk size. Is there a recommendation on a good > > > size to use considering that we are running informix as follows: > > > > > > Informix 11.70.FC7W2 > > > Primary OLTP Envirnoment mixed with reporting > > > Solaris 10 > > > Currently using 440 2GB chunks across 11 DB Spaces. > > > > > > Any suggestions would be greatly appreciated. > > > > > > Thank You, > > > > > > --Dave > > > > > > --089e0158ace071e35c04eb288f8f > > > > > > > > > > > > > --bcaec5486346dad3a704eb32d135