[popesy]

I am sure this is a quick question

With the mapping of storage to a vhost (LPAR) using the 'mkvdev -vdev..' command, how do I know that the hdisk I am mapping to the vhost will have affinity to a specific VIOS?

What I am trying to determine is which is the primary VIOS in steady state for that LPAR and also in a failed over state for the same LPAR. Is it merely a case of the steady state being the VIOS that I first ran the mkdev command on?

I have found a command 'mpstat -h' (not yet tried this).

Thanks.

JP

[seth]

Hi popesy

mpstat (-h flag does not exist or is at least not documented) Collects and displays performance statistics for all logical CPUs in the system. So how shuld that help you on the quest finding your "primary" VIO server.
There is no quick and easy info on that so you better write that when you create the LPAR LUNs in some sort of documentation or your lost! You may keep them in the head or think I always take VIOx as primary. It may wor a while but as your infrastructure and IT team grows this is something that should be documented!

Well lets assume you have to VIOS and one LPAR, on that LPAR a hdisk2 for example and want to know which VIO server serves it as "primary" and which one is the "backup".
Here the example:

root@i21lpar1:/ > lspath
Enabled hdisk0 vscsi0
Enabled hdisk1 vscsi1
Enabled hdisk0 vscsi2
Enabled hdisk1 vscsi3
Enabled hdisk2 vscsi4
Enabled hdisk3 vscsi4
Enabled hdisk2 vscsi5
Enabled hdisk3 vscsi5

You see hdisk2 (in ideal conditions) over 2 ways vscsi4 and vscsi5.

root@i21lpar1:/ > lspath -AHE -l hdisk2 -p vscsi4
attribute value description user_settable

priority 2 Priority True

OK so you know now vscsi4 is the backup device

root@i21lpar1:/ > lspath -AHE -l hdisk2 -p vscsi5
attribute value description user_settable

priority 1 Priority True

Bingo! vscsi5 is the device you have to trace!

root@i21lpar1:/ > lsslot -c slot
# Slot Description Device(s)
U9117.MMA.068A540-V3-C0 Virtual I/O Slot vsa0
U9117.MMA.068A540-V3-C2 Virtual I/O Slot vscsi0
U9117.MMA.068A540-V3-C3 Virtual I/O Slot vscsi1
U9117.MMA.068A540-V3-C4 Virtual I/O Slot vscsi2
U9117.MMA.068A540-V3-C5 Virtual I/O Slot vscsi3
U9117.MMA.068A540-V3-C6 Virtual I/O Slot ent0
U9117.MMA.068A540-V3-C7 Virtual I/O Slot ent1
U9117.MMA.068A540-V3-C8 Virtual I/O Slot vscsi4
U9117.MMA.068A540-V3-C9 Virtual I/O Slot vscsi5

So you see vscsi5 has client slot number 9 (C9).
Now log on to your HMC, gor to manage profiles of the lpar you just logged in and look into the active profile on virtual adapters there we have a "Adapter ID" this represents the Client slot ID. Look at number "9" in the same row the next filed shows you the connected VIO Server. If you want to know which disk the client hdisk2 on the VIO is then Note the "Connecting Adapter" in the same row and log into the VIO server which was shown in the last step.
In my case its i21vio2 and my Connecting Adapter is "19".

lsdev -slots | grep C19
U9117.MMA.068A540-V2-C19 Virtual I/O Slot vhost2

So we found out the right vhost (vhost2)

lsmap -vadapter vhost2
SVSA Physloc Client Partition ID
--------------- -------------------------------------------- ------------------
vhost2 U9117.MMA.068A540-V2-C19 0x00000003

VTD vtscsi2
Status Available
LUN 0x8100000000000000
Backing device hdisk8
Physloc U789D.001.DQD9Y01-P1-C2-T1-W50060E8010051029-L6000000000000

VTD vtscsi3
Status Available
LUN 0x8200000000000000
Backing device hdisk9
Physloc U789D.001.DQD9Y01-P1-C2-T1-W50060E8010051029-L7000000000000

So our VIO2 is configured that it sees each device over two FC adapters that's the reason why we see 2 disks at the vhost device. To find the currently active device you need to go back to the client and get the pvid from hdisk2

root@i21lpar1:/ > lspv
hdisk0 00c8a5404c2ee5d5 rootvg active
hdisk1 00c8a5404c2eea3b swvg active
hdisk2 00c8a5404c2efd45 ics1e2evg active
hdisk3 00c8a5404c2f01af ics1e2evg active

then you grep for this id on the VIO server:

padmin@i21vio2:/home/padmin > lspv | grep 00c8a5404c2efd45
hdisk8 00c8a5404c2efd45 None
padmin@i21vio2:/home/padmin > lspath | grep hdisk8
Enabled hdisk8 fscsi0 50060e8010051021,6000000000000
Enabled hdisk8 fscsi2 50060e8010051029,6000000000000

this shows you the the corresponding fcs Adapter.
with

padmin@i21vio2:/home/padmin > lspath -dev hdisk8 -pdev fscsi2 -lsattr
attribute value description user_settable

scsi_id 0x792c13 SCSI ID False
node_name 0x50060e8010051029 Node Name False
priority 1 Priority True
padmin@i21vio2:/home/padmin > lspath -dev hdisk8 -pdev fscsi0 -lsattr
attribute value description user_settable

scsi_id 0x6f1813 SCSI ID False
node_name 0x50060e8010051021 Node Name False
priority 2 Priority True

you see that fcs2 is the primary adapter for the client disk hdisk2.
Be cautious this is an environment with default MPIO Fiber Disk Driver enabled. If you use any other storage devicedriver like Hitachi HDLM or SDD from IBM you might have to handle the disks on the VIO in some other way (lspath will not work as expected for example). Anyway you see this is all but easy to get to this info so you better prep your excel documents for lot of VIO-LPAR documentation...

Cheers seth

Edit: made it more readable

[popesy]

Seth

Cheers for this, it is absolutely what I was after.

All path priorities are set to '1'. That being the case I understand that that means the primary one is the vscsi adapter with the lowest numeric value assigned to it i.e. out of vscsi0 and vscsi1 the primary will be vscsi0.

Many thanks for your help with this,

JP

[TMcGivern]

Seth.. I like your response (was not familiar with lspath -AE
WHen I run it on my systems Dual VIO, the responses come back where every path is priority 1..

What's that telling me?

lspath | while read paths
do
set $paths
echo $2 $3 $(lspath -AEO -l $2 -p $3)
done
hdisk0 vscsi1 #priority 1
hdisk0 vscsi2 #priority 1
hdisk1 vscsi1 #priority 1
hdisk1 vscsi2 #priority 1

so both VIO servers are used equally? That'd be nice, I think...

[seth]

Hi

It is nothing bad to have all on priority 1
We balance our IOs across both VIOS to reduce the IO Load on the VIO FCS Adapters.
Priority 1 means "always use the first path found, if this doesn't work take the other path". Lets take your output as example:
hdisk0 vscsi1 #priority 1 ->this path is used for hdisk0
hdisk0 vscsi2 #priority 1 -> if above path fails this one ist taken
hdisk1 vscsi1 #priority 1
hdisk1 vscsi2 #priority 1
Same rules apply to the hdisk1, due vscsi1 is taken in this case for both disks both IO requests for this disks would go to the same VIO server. That's nothing bad in small environments. If your SAP for instances are running this way you may have problems sending all IO requests only to the first VIO.
Here a example from our environment:
Enabled hdisk2 vscsi4
Enabled hdisk2 vscsi7
Enabled hdisk3 vscsi4
Enabled hdisk3 vscsi7
root@i26lpar2:/ > lspath -AEO -l hdisk2 -p vscsi4
#priority
2
root@i26lpar2:/ > lspath -AEO -l hdisk2 -p vscsi7
#priority
1
root@i26lpar2:/ > lspath -AEO -l hdisk3 -p vscsi4
#priority
1
root@i26lpar2:/ > lspath -AEO -l hdisk3 -p vscsi7
#priority
2
See the difference? vscsi4 goes to vio1 and vscsi7 goes to vio2, for the hdisk 2 the IO are sent to vio1 per default and for hdisk3 the default IO goes to the vio2.

Hope that helps you understanding it!

Cheers seth

[TMcGivern]

Thanks, that did help.
Now, seeing as they are all priority 1, and I'd like to move the order around, more like yours..
Is there a chpath or chdev command that will change that priority?
I see on the lspath, that the value is "TRUE", implying to me I can change it some how.

[seth]

Hi
This can be done easly with chpath, see following example:
chpath -l hdisk35 -p vscsi4 -a priority=1
chpath -l hdisk36 -p vscsi4 -a priority=2

chpath -l hdisk35 -p vscsi5 -a priority=2
chpath -l hdisk36 -p vscsi5 -a priority=1

Cheers seth