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Informix read & write only in one disk.....

Sritharan
Valued Contributor

Informix read & write only in one disk.....

Hi,

need some (a lot)help

We are using HPUX 11.11 (clustered server) L class and FC60 disk array. We are using it as Informix database server. We have 8 physical disk. The problem is when the database read & write its only doing on one disk.
When we use iostat we can see only one disk is been use.

How do we make it read & write on all the disk ??
Is the configuration is done on the HPUX or the Informix ??

Thanks
Sri
Known is a drop...unknown is an ocean -> quote from a movie
8 REPLIES
A. Clay Stephenson
Acclaimed Contributor

Re: Informix read & write only in one disk.....

Without know how you set up your LUN's on the FC60 there is no way to answer your question. If you have set the array up as one big LUN then it appears to the host to be going through one physical device when in fact it's using multiple disks in the array.

Please add a few details about your current array configuration. LUN's, RAID Level, ...
If it ain't broke, I can fix that.
Jordan Bean
Honored Contributor

Re: Informix read & write only in one disk.....

Writing from an Ifx7 background, Informix doesn't distribute its databases or tables evenly over all available dbspaces (logical or physical volumes). The default behavior is to fill up each dbspace sequentially.

Similarly, LVM will not evenly distribute data in a un-striped logical volume that spans many disks.

Unfortunately I'm not familiar with the FC arrys. What is the RAID level? Are you using LVM? Or is Informix using each raw disk directly?

I'm willing to wager my points that you have each dbspace on a single disk... and the one active disk is the first dbspace.
Sritharan
Valued Contributor

Re: Informix read & write only in one disk.....

Hi,

Sorry for the late response :-)

Please check the attachment for more details,

We are using using Informix 9.3



TIA
Sri
Known is a drop...unknown is an ocean -> quote from a movie
harry d brown jr
Honored Contributor

Re: Informix read & write only in one disk.....



OK, that attachment wasn't very useful.

Try providing the following:

bdf
vgdisplay -v vg*
ioscan -fn

then tell us which Logical Volume (LV) that informix is using.

From the attachment you provided I did see that VG00 has TWO disks in it.

live free or die
harry

Live Free or Die
Pete Randall
Outstanding Contributor

Re: Informix read & write only in one disk.....

Sri,

I can't open your attachment but I'll hazard some guesses anyway. We've got a similar environment: FC60 array configured in RAID 0/1 with Informix 7.31. With RAID 0/1, we've got 10 luns of 18 GB each and their mirrored counterparts (20 physical drives). In order to distribute I/O across this space we have to assign particular tables to particular dbspaces which are in turn assigned to particular LUN's. There is no way of making this happen automatically - that I'm aware of, that is.

Hope this helps,
Pete

Pete
Sritharan
Valued Contributor

Re: Informix read & write only in one disk.....

Hi,

/ifmx - informix lvol
we are using vg01 for the informix
we are using Informix 9.3 and raid 0/1
I have included the info,Pete

TIA
Sri
Known is a drop...unknown is an ocean -> quote from a movie
Pete Randall
Outstanding Contributor

Re: Informix read & write only in one disk.....

Sri,

Ok, you've got 25 lvols of 2GB each. These equate to what Informix class chunks. Chunks are assigned to dbspaces. Tables are put in dbspaces. In order to distribute your I/O, you're going to need to move some tables from one of the dbspaces that's occupying a chunk which equates to an lvol that resides on /dev/dsk/c7t0d0 to an lvol that resides on /dev/dsk/c7t0d1. Use lvdisplay -v |more to see which lvols occupy which physical device.

Does this help?

Pete

Pete
Pete Randall
Outstanding Contributor

Re: Informix read & write only in one disk.....

Sorry, that should have read "what Informix CALLS chunks" not class. Damn fingers!

Pete

Pete