topic Re: dual controllers in Disk Enclosures

dual controllers

Kevin Wright — Wed, 20 Sep 2000 17:59:37 GMT

currently on a AutoRaid 12H, there is one scsi bus from the server to one array controller, and then that controller is linked (like a daisy chain) to the other controller. I want to run an scsi bus from the server to each array controller for redundancy and speed... What do I need to do to load balance the controllers, whoever installed the hparray/ARMServer software did not install the man pages..any links out there for commands like arraycfg???

Re: dual controllers

Patrick Wessel — Thu, 21 Sep 2000 06:04:11 GMT

Kevin,
You balance the load with the LVM. Use for the 'half load' the X controller as the primary path and for the rest the Y controller. For the AutoRAID array is this a useful link for information: http://www.hp.com/essd/model12H_index.html

Re: dual controllers

Andreas Voss — Thu, 21 Sep 2000 06:11:46 GMT

Hi,

load balancing can be done at volume group level.
If you do a vgdisplay -v vgXX you can see at Physical volumes the PV Names. One of them should be listed as '/dev/dsk/c?d?t? Alternate Link'.
You can modify the paths by using vgreduce/vgextend.
Example:
AutoRaid LUN 1 bound to vg01
Controller X at SCSI 14 / Instance 8
Controller Y at SCSI 15 / Instance 9
Device for X = /dev/dsk/c8t14d1
Device for Y = /dev/dsk/c9t15d1
When creating vg01 with /dev/dsk/c8t14d1
you can add alternate link with:
vgextend vg01 /dev/dsk/c9t15d1
To change the alternate link first remove the /dev/dsk/c8t14d1 with:
vgreduce vg01 /dev/dsk/c8t14d1
This will automatically switch to /dev/dsk/c9t15d1 as primary.
Now add /dev/dsk/c8t14d1 again with:
vgextend vg01 /dev/dsk/c8t14d1
and you will now get the /dev/dsk/c8t14d1 as the alternate link.

Regards

Andrew

Re: dual controllers

Insu Kim — Thu, 21 Sep 2000 08:38:36 GMT

Your system has connections for one disk array, two controllers, and one scsi bus but for high availability like redundancy, speed what you mentioned, you need connections for one disk array, two controllers, and two scsi buses.

Requirements are one more scsi adaptor, scsi cable on host side.
This enables you to access your data from unexpected controller, scsi bus disaster, and host scsi adaptor failure.

Each disk array controller should be connected one channel for better load balancing.
Load balancing can be done at LVM level as somebody else said.