Re: ra_pages and io rate

Hi Art, Thank you vrymuch for your reply. I am trying to opimize the sequental scans in a datawarehouse environment.My disk subsystem is emc , raid 10 . I have 1 hba and can transfer 100MB. per second. With oracle , seq. scans can read 1mb. per read operation and with these value i can full scan tables by issuing low number of io requests . If informix reads 2 or 4kb. on each read , doesnt it mean that it must request more io operation? Kind Regards, hope "Art S. Kagel" <kagel@bloomberg.net> wrote in message news:<42C1CA58.7020501@bloomberg.net>... > hopehope_123 wrote: > > Hi , > > > > When i strace the aio vps , no matter what the value i set for ra_pages > > , the pread system calls always request 2kb. disk blocks form the disk > > subsystem . How can i achive high io rates with informix. (For instance > > , in oracle by using db_file_multi_block_read_count , i can achive 1mb. > > per read.) > > Do NOT try to tune Informix like you would Oracle! Informix ALWAYS reads > and writes either a single disk page (2 or 4K prior to IDS 10.00), performs > a 'bigread' of 4 pages (8K or 16K), or does a block write of 4 pages at a > time. Period. > > Are you having some performance problem? Post the symptoms and we'll > suggest some onstat output and onconfig parameters we want to review for > you. Don't forget to describe your system/environment including: > Platform & OS (including version), IDS version (including fixpack level), > type of disk farm (JBOD, RAID*, etc.) along with the symptom. > > If you are just trying to increase read-ahead efficiency, not to worry IDS > is pretty efficient at it without help. 8-O > > Art S. Kagel