HP-UX Kernel Performance Tuning For Informix

[Amit Dixit_2]

Hi Stephen,
Probably I might go for another questions

I created RAW filesystem(no entry in fstab)
I do have OnlineJFS installed on my system
now tell me how can I optimize r/w on the
disk.

So as to have better disk performance from
Informix.

Thanks
Amit.

[Sridhar Bhaskarla]

Hi Amit,

There is no such thing called 'raw filesystem'. It is either 'raw device' or 'filesystem'. For ex., under LVM when you do

lvcreate -n lvol1 -L 2048 vg01

and use /dev/vg01/rlvol1 with informix, then you are using raw device.

But if you continue to further and do

newfs -F vxfs /dev/vg01/rlvol1
mount /dev/vg01/lvol1 /somefs

and use the directory /somefs, then you are using a filesystem.

OnlineJFS works only with filesystems. It can't help raw devices.

You will have to consider striping, faster HBAs, better storage systems etc., to improve performance of the raw devices. You don't have much choice to manage data on raw devices. It is to be managed by the software and in your case it's informix.

-Sri

[Bill Hassell]

When you configure Informix, you specify raw disk volumes, or filesystems. A raw disk volume would look like this:

/dev/vg01/rlvol7

or whatever lvol's you are allocating to Informix. The majority of Informix installations use raw volumes, not filesystems. NOTE: you will degrade performance if you specify /dev/vg01/lvol7 (note the missing "r") for Informix. Raw I/O means that Informix handles all the disk activities. Parameters like fs_sync are meaningless because have no database files, just raw lvols. The only improvement for disk I/O is to use a (pricey) disk array with fibre connections and massive (gigabyes) of cache RAM in the array.

Now using raw I/O requires careful design on a backup method. There are no files, just volumes with long streams of random bits. One way (if you have extra disk space) is to export the database and then use conventional backup tools like fbackup on the exported data files. Another is to use dd but this is very risky as there is no way to identify what is on the tape or how to put it back without very careful record keeping. Commercial backup tools like HP's OmniBack (ie, Data Protector) has provisions to backup raw volumes.