I/O Load Thorugh Multipath

[Trng]

Dear Gurus,

we have installed EMC powerpath on our HPUX 11.23 .Erlier we were using PV Links ..can anybody explain how to check the load(i/o rate) on each path ?...Because we need to test what is the performance improvement after installing multipath ...

rgds
trng

[Bulent ILIMAN]

i am not familiar with EMC boxes but in hpux point of view you can use

sar -d 1 20

to see your disk dev performance for 1 sec intervals and 20 repeats

you can set those parameters, send output to file and analyze it also

[Trng]

Hi: my requiremnet is ,i have a lun c0t0d0 ,other path for same lun is c1t0d0,c2t0d0,c3t0d0 ...i want to know how to check i/o is ditrributed over these four paths or not (as per multipath softwares are for distributing the load through diff paths--how to prove this ?)

rgds
trng

[Bulent ILIMAN]

sar command can help you about this

you can ask EMC about their software also

[Binubaby]

Hello
Use EMC Powerpath command

#powermt display dev=all

This output will give you detailed information.

BB

[Turgay Cavdar]

You should first check your load balancing policy (it shouldnt be basic failover).


Powermt command doesnt show IO statistics. The man page talk about "Stats IO/sec" but i couldnt see it in the output.


Stats IO/sec
Value: Non-negative integer
This field is blank for powermt display, unless it is used with the every parameter. Subsequent powermt display terations display the average number of I/Os sent across this bus each second.



You can still see the load distribution with sar:
# sar -d 1 345345 | grep t0d0 (i assume your disks are c1t0d0,c2t0d0,c3t0d0)

[Trng]

Dear Gurus,

Awaiting your valuable answers ....

Let me explain once again ...
i have an HPUX box with EMC storage connected .i was using only (TWO FC CARD ,so alt link with only one per FC) for my all VG's ..As everyone knows(theorotically) Multipath software will do load balancing and distribute the load to all paths ( I have two FC cards ,so each disk will have 4 paths after installing powerpath with claropt policy) ....

My question is; how to check Load is ditributed over four paths ?.sar -d will show only load over one path ..



rgds
trng

[TTr]

If you have glance installed, look at the i/o screens. There are screens for LVs and PVs and you can see the i/o on the physical volumes.

[Bulent ILIMAN]

if you run sar without any device name, then it will give you All the devices IO,
if alternate pathes are not included into VG as alternate pathes then it is not possible to see any IO on that path you must first use vgextend,

if a path in the vg has been showing 0(zero) IO then we can say that load balancing is NOT working.

just send
vgdisplay -v

for your VGs and

sar -d 2 200

[Earl_Crowder]

Trng,

powermt display every=10

This command will show the status of HBAs with a column with "IO/Sec" listed, refreshed every 10 seconds.

powermt display dev=all, look for policy= for each device to see what the load balance policy is.

man page for powermt has more information on load balancing policies.