VIO servers and EMC hdiskpower -NEED HELP

[oliverbeat]

Hello,

I would like to install new vio servers using Powerpath/EMC disks.
I know how to install powerpath etc... on vios servers but what I don't really understand is the fact that 2 vio servers can have access to the same LUN (Disk EMC ) ? I am referring to the TEC doc EMC, they said: "P5 system can have multiple VIOS LPARs providing access to the same LUN for the same VIOC for Standard Device configurations (no multipathing) and multipathing devices under the control of PowerPath and MPIO. For Standard Device and PowerPath configurations, the VIOS device reservation setting "reserve_lock" will need to be changed (via the chdev command) to "no". For MPIO configurations the VIOS device reservation setting "reserve_policy" will need to be changed (via the chdev command) to "no_reserve"."

I am trying to understand but I am confused !!! I need your help !
Example if I have 2 vios connecting to the same hdiskpower
how I can create my vhost on both vios server with the same configuration ? is it really possible ?
because it is the same disk EMC and on each vio I should create my vhost (before I have to create the LV etc...)

I am very confused... with scsi disks it is more easy as we are using to physical disk different and I have to mirror my volume group on the client.

But if with EMC disks 2 vio server can have access to the same disk, it means that on my client I will not do any mirroring again and it is a very good news because in the case I loose one vio server I will still have access to my disks through the other vio without any errors hdisk (no more hdisk missing!!!)


But I don't know how to do it. If someone have already confugred vios servers using the same EMC disk and create the LV for the vohst how you do it !!!

Thanks in advance

 

[p5wizard]

I haven't yet any experience with this setup. But here is my $.02 worth:

I believe you have to host the whole LUN to the client partitions on both VIO servers, and NOT create a VG on the VIOS from the EMC LUNs and host an LV in that VG as a virtual disk to a client.

That way, you can provide a virtual scsi path through both VIOSs to the same LUN on the EMC, provided both VIOSs do not "reserve" the disk in the EMC box. Hence the need to set reserve_lock=no for emcpower disks or reserve_policy=no_reserve for MPIO disks on the VIOSs.

Your client partition can then use an MPIO configuration for the EMC LUN through the two paths via the 2 VIOSs for every LUN.


HTH,

p5wizard

 

[hfaix]

I have not done this with emc, but I have done it with IBM ESS (Shark) disk.

The key for doing it with ESS is reserve_policy=no_reserve (and both vio's must show the same pvid for the hdisk). As p5wizard mentions, you will need to use full hdisks not lv to client lpars.

 

[oliverbeat]

Thank you for your replies.
hfaix> you have to vio on ESS/SAN and connecting to the same LUN (with the option reserve_policy=no?reserve)- is that right ?

So when you have create the vg on the vio1 (mkvdev command( did you do the same on the vio2 or how did you do to have the same things on vio1 and vio2 ?

You said that we cannot create LV on vios for ESS/SAN disks / so it means that we cannot cut the ESS disks on several luns (lvs) = virtual disk for the client?

Thanks in advance for your answer.
Cheers.

 

[p5wizard]

You DON'T create any VG on any VIOS. You make a virtual device of every SAN disk the VIOSs see. You do that on both VIOSs and you need to make sure the VIOSs do not reserve the disks on the SAN storage server in order for both VIOSs to be able to read/write to the SAN disks.

On both VIOSs, you attach the virtual disks to the vscsi host adapter to make them visible to the client partition's vscsi client adapters which are linked to both the VIOSs vscsi host adapters. The client then gets to see 2 paths for the luns via both the VIOSs.

The client partition then creates a VG on the vscsi disks it sees as MPIO disks.

If you need to host several clients' storage, you need to assign every client's SAN volumes to the VIOSs first.

So no, you don't create a VG and cut the SAN volumes into smaller LVs to host them to client partitions if you want MPIO on the clients. You can do it like that with LVM mirroring on the clients, but then you need double the SAN storage: 1 copy for each of the VIOSs.


HTH,

p5wizard

 

[oliverbeat]

Thank you very much for your help !
I will test this next week and we will how it works.
Cheers.