Ideal disk blocksize for Informix on Linux

Hi Gurus, I have to install Informix IDS 10 on a Red Hat EL4 box, it's an HP DL 385 with a P600 disk controller which features hardware RAID. When setting the hardware RAID on the 5 disks that I've decided to reseve for the database, I am offered to specify the blocksize (8,16,32,64,128 Kb). AFAIK Informix default block size is 16Kb, should I set the DB volume blocksize accordingly? What if the volume containing the Informix dbspaces contains also some (non-OS) filesystems, is the impact on filesystems' performance significant? Any experience about this? Thanx in advance Rupan3rd (from Italy)

depends on the version; the db writes in pages it can do 1 up to 16 pages at a time for linux is pagesize 2k 16*2k =32k = maxiosize. (at least V9.3 and lower do V9.4 and bigger; dono specially with variable pagesizes you have to test this; eq disable lru cleaning load data force checkpoint and check with iostat or something the # of req and the troughput, based on that you should be able to work out what the maxiosize is.) rule of the thumb used to be 2 * maxiosize to avoid split writes meaning in your case 64 KB. or 128... Superboer. Rupan3rd schreef: > Hi Gurus, > > I have to install Informix IDS 10 on a Red Hat EL4 box, it's an HP DL 385 > with a P600 disk controller which features hardware RAID. > > When setting the hardware RAID on the 5 disks that I've decided to reseve for > the database, I am offered to specify the blocksize (8,16,32,64,128 Kb). > > AFAIK Informix default block size is 16Kb, should I set the DB volume blocksize > accordingly? What if the volume containing the Informix dbspaces contains also > some (non-OS) filesystems, is the impact on filesystems' performance > significant? > > Any experience about this? > > Thanx in advance > Rupan3rd (from Italy)

Thanx a lot. I am contacting Informix support in parallel, will post their answer here. Thanx! R. Superboer wrote: > depends on the version; > the db writes in pages it can do 1 up to 16 pages at a time > for linux is pagesize 2k 16*2k =32k = maxiosize. > (at least V9.3 and lower do V9.4 and bigger; dono specially with > variable pagesizes > you have to test this; eq disable lru cleaning load data force > checkpoint > and check with iostat or something the # of req and the troughput, > based on that > you should be able to work out what the maxiosize is.) > > rule of the thumb used to be 2 * maxiosize to avoid split writes > meaning in your case 64 KB. or 128... > > Superboer. > > Rupan3rd schreef: > > >>Hi Gurus, >> >>I have to install Informix IDS 10 on a Red Hat EL4 box, it's an HP DL 385 >>with a P600 disk controller which features hardware RAID. >> >>When setting the hardware RAID on the 5 disks that I've decided to reseve for >>the database, I am offered to specify the blocksize (8,16,32,64,128 Kb). >> >>AFAIK Informix default block size is 16Kb, should I set the DB volume blocksize >>accordingly? What if the volume containing the Informix dbspaces contains also >>some (non-OS) filesystems, is the impact on filesystems' performance >>significant? >> >>Any experience about this? >> >>Thanx in advance >> Rupan3rd (from Italy) > >