Informix I/O performance

Informix version: Informix 11.5FC4 Operating system: SunOS 5.10 sun4v sparc (64bit) SAN: ENC connecrted through HBA Raid level: 10 File System: Ext3 We 've neither using raw-devices nor configured the KAIO. And running about 12 databases of OLTP nature, having a couple of big tables with lot of indexes on them. We need to know that for OLTP databases with frequent read & writes what of the followings would be better to use and what are hazards: 1- KAIO (also the guidlines for change in existing number of AIO VPs) 2- Journaling (disabling it is recommended on this forum for performance gain, but it is said that enabling it makes the system more safe) Second question is about temp dbspace; how can we distribute more than one temp dbspaces, and other dbspaces to reduce I/O contention as their are several databases running on same machine and using same SAN. regards, Kamran

On my phone so the quoting is not good. Introducing my comments with 'ASK'= . See below: Art=20 -----Original Message----- From: KAMRAN HAQ <khaq@i2cinc.com> Sent: Tuesday, June 23, 2009 5:24 AM To: ids@iiug.org Subject: Informix I/O performance [16129] Informix version: Informix 11.5FC4=20 Operating system: SunOS 5.10 sun4v sparc (64bit)=20 SAN: ENC connecrted through HBA=20 Raid level: 10=20 File System: Ext3=20 We 've neither using raw-devices nor configured the KAIO.=20 And running about 12 databases of OLTP nature, having a couple of big table= s=20 with lot of indexes on them.=20 We need to know that for OLTP databases with frequent read & writes what of= =20 the followings would be better to use and what are hazards:=20 1- KAIO (also the guidlines for change in existing number of AIO VPs)=20 ASK - KAIO is enabled by default, but, you need to enable DIRECT_IO for it = to work for COOKED filesystem chunks. RAW is better? But not by much (5%).= If you enable DIRECT_IO then either start with 4 AIO VPs and tune or star= t with 2 and turn on AUTO_AIO and let the engine tune them for you. 2- Journaling (disabling it is recommended on this forum for performance ga= in,=20 but it is said that enabling it makes the system more safe)=20 ASK- NO JOURNALED FILESYSTEMS! You should not be using EXT3 even. Perform= ance isn't as good as a non-joournaled FS and IDS does its own logging whic= h is far safer than the journaling anyway. IDS's writes are all either und= er O_SYNC or O_DIRECT to pre-allocated disk space so the journaling gains y= ou nothing and costs you speed. Also some journaled FSs are unsafe - EXT3 = with writeback enable and EXT4 always are two such. See the web on the iss= ues. Second question is about temp dbspace; how can we distribute more than one= =20 temp dbspaces, and other dbspaces to reduce I/O contention as their are=20 several databases running on same machine and using same SAN.=20 ASK - Get the database off the shared SAN! Is ounds trite but it is the ON= LY solution. Database and filesystems have VERY different access patterns.= Trying to share a database's storage with other apps is a bad idea and a= dding multiple machines to the mix is deadly. I don't care what the SAN ve= ndors say on this one. regards,=20 Kamran=20 ***************************************************************************= ****=20 Forum Note: Use "Reply" to post a response in the discussion forum.=20