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Informix KAIO enabling

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Stojcevski Dejan
Regular Advisor

Informix KAIO enabling

Currently we are running Informix IDS 2000 Version 9.21.HC4 on HP-UX 11.00 OS. Machine is rp7400 with 4 CPU's and 4GB of RAM.
1. Has somebody tried to enable KAIO threads on VCPU with this kind of configuration? Share some experience.
2. Currently we have 16 AIO's running and the data is stored in raw sapace. We do not use a cooked files for this. Will KAIO be of some benefit to us? What is the ratio of performance boost if any? What is better: increasing the number of AIO's of enabling KAIO on the system?
3. Is it secure? We do have only production servers so I do not want to find later on that some of the data is corrupted or backup is not working ... I have noticed somewhere that KAIO is not working as it should on HP-UX boxes!

Procedure is well known: pseudo async driver is already in the kernel and HP-UX is supporting the KAIO's (as written in release notes). So basically I am looking for some tried solutions by other users and their's recomendations!
Carpe Diem
Fischer Klaus
Occasional Visitor

Re: Informix KAIO enabling

HP-UX and Informix is like having a Porsche with used(closed) hand-brake.

We are using KAIO since last year without any problems (HPUX11.00)

1. Please check if the asyncdsk driver is installed and used in the drivers of the kernel (SAM).
2. set the env. variable KAIOON=1 and IFMX_HPKAIO_NUM_REQ=2300
3. Check if /dev/async exists.
If not create as root a.) for using HP redundancy or mirroring: /usr/bin/mknod /dev/async c 101 0
b.) for using Informix mirroring or no mirroring: /usr/bin/mknod /dev/async c 101 4
4. chmod 0666 /dev/async
5. create follow entry in the /etc/prigroup file: informix MLOCK
6. execute /sbin/rc1.d/S400set_prvgrp start

7. reduce the AIO's to 2

8. after you restart informix check first the
online.log if KAIO is started. With onstat -g iov there should be lines with kio class
Stojcevski Dejan
Regular Advisor

Re: Informix KAIO enabling

The procedure is well known except for the following:
1. What the variable IFMX_HPKAIO_NUM_REQ stands for and what if I do not set it to some value?
2. What's the story with the /etc/prigroup?
3. Do you have ANY problems after enabling KAIO on your system - inconsistent backup, some side effects etc ... I am asking this because we do have only production server and I want to be absolutely sure about this issue that is not to have aby problems after enabling KAIO's.
4. What performance boost did you have after enabling KAIO's on yor system? Did you get Porche out of the Clio?
Carpe Diem