Rules for VSCSI accessing data disks

[polani]

Guys

I need one more advice from you , regarding VSCSI . I have just implemented a VIOS setup with one VIOS and a large number of client Lpars.

I have used same VSCSI 9 (let's say vscsix ) on each client lpar to mapp disks for rootvg as well as disks for datavg.

In my environment, rootvg is offcource on a scsi disk , being exported from VIOS servers , while datavg are on san disk ( again physically attached to FC adapters of VIOS servers).

Question is that , what is best stretegy... Technically possible to use same vscsi for rootvg and datavg , but what is best practise ( and also from performance point of view)...

I have searched manuals and redbook , nobody says about different VSCSI for rootvg and datavg ...

For me , solution works fine and off course more complexity in management , if i retain with single vscsi strategy for each client lpar....

Any comments or suggestions ...


Polani,

Here comes polani Once again!!!

P690 Certified Specailist
HACMP & AIX Certified Specailist
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[p5wizard]

IMHO question of personal preference...

I use different VHOST/VSCSIs pair for rootvg and data disks, but it is more complex

And also you have to take care because VSCSI dual pathing sometimes assigns extra paths to incorrect hdisks, especially if you present newly created LUNs via different VSCSI adapters, VSCSI client doesn't know which LUN is which, so it uses the SCSI address of the different VSCSI disks (810000000000, 820000000000, ...) to match paths.

I once had a data LUN being identified as an extra path to a rootvg LUN (all on SAN)... Not something I want to see repeated!

Best practice in this setup is to cfgmgr via one VSCSI adapter first, make hdisks into volume group, or extendvg the hdisks into a volume group, and then cfgmgr second VSCSI adapter to identify 2nd paths correctly.

[off topic]
remember to set hcheck_interval to 60 (non zero) for SAN-VIOS-MPIO hdisks in order for MPIO to rediscover access to failed paths after rebooting one of your VIOSs
[/off topic]


HTH,

p5wizard