performance problem using host-based-mirroring over two computer centers

[OSY Unix 1-4-2 (A-Team)]

Hi admins :-)

We have some performance problem using host-based-mirroring over two computer centers.

We have two data centers, in each there is a L-Class HPUX11.i, two Brocade FC-switches and one VA7100. Between the switches there are two InterSwitchLinks, so each server can also 'see' the storage in the other data center. Using LVM host-based-mirroring for an shared oracle volumegroup (rawdevices) we got a two cell ServiceGuard-Cluster with Oracle-Parallel-Server functionality.

But now we discovered a slow io rate during LVM-mirroring. A simple file creating using dd-command needs much more time (times 4) on mirrored disks than on the local disks ! And it is hard to discuss this with angry application people. So my question to you : do you have any suggestions or ideas where to look ? Which parameters to change ? How to increase performance ? How to get more detailed infos where exactly we got the problem ? What to change in hardware ?

Any information is welcome ! Thanks for your answers to my mail, i will summarize as soon as possible !

Thanks,
An admin in trouble
Roland
:-)

[Duncan Edmonstone]

Hi Roland,

First place I'd look is your SAN config:

1. Have you checked that all devices are in fabric login mode, and that nothing is using FC-AL (loop topology). FCAL provides 100Mb/s bandwidth shared between all devices. Fabric login, or fabric mode provides 100Mb/s to each device.

2. Your two ISL links - what type of links are these? Longwave or shortwave GBICs? What type of fibre provides the connections? 9/125, 50/125 or 62.5/125? Or are you using DWDM?

3. Have you checked for execssive error logging on the switches? -Sorry I don't have my brocade notes with me so I can't remember the commands to gather this info...

Next we should probably take a look at your logical volume configuration - can you post a vgdisplay for one of your mirrored volume groups, and a lvdisplay for one of the volumes in that volume group.

That should at least give us some food for thought...

Duncan

[Duncan Edmonstone]

Also Roland you should consider posting this query in the Storage forum here:

http://forums.itrc.hp.com/cm/FamilyHome/1,,120,00.html

Not all the experts there necessarily read the HP-UX forum posts...

HTH

Duncan