KyleTucker
1 Copper

EMC PowerPath on Linux and Net-SNMP

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Hi all,

I am new to PowerPath on Linux and this forum. I am trying to determine IOPS on a Linux database server and Net-SNMP is reporting back 8 devices from a VNX5300, each "pair" having a letter and a matching one ending in 1.

.1.3.6.1.4.1.2021.13.15.1.1.2.67 = STRING: emcpowerd

.1.3.6.1.4.1.2021.13.15.1.1.2.68 = STRING: emcpowerd1

.1.3.6.1.4.1.2021.13.15.1.1.2.69 = STRING: emcpowerg

.1.3.6.1.4.1.2021.13.15.1.1.2.70 = STRING: emcpowerg1

.1.3.6.1.4.1.2021.13.15.1.1.2.71 = STRING: emcpowere

.1.3.6.1.4.1.2021.13.15.1.1.2.72 = STRING: emcpowere1

.1.3.6.1.4.1.2021.13.15.1.1.2.73 = STRING: emcpowerf

.1.3.6.1.4.1.2021.13.15.1.1.2.74 = STRING: emcpowerf1

Each of these has it's own counters and they are not exact but are very close. I wasn't sure if each of these is legit and load balancing is in play or if this is just a by-product of how PowerPath works. I do know fdisk doesn't show any partitions for the devices ending in 1, so that's where I am most confused.

Any help or guidance appreciated.

- Kyle

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umichklewis
4 Beryllium

Re: EMC PowerPath on Linux and Net-SNMP

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Can you print the output from "powermt display dev=all"?

Thanks!

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KyleTucker
1 Copper

Re: EMC PowerPath on Linux and Net-SNMP

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# powermt display dev=all

Pseudo name=emcpowerd

CLARiiON ID=APMxxxxxxxxxxx [localhost]

Logical device ID=600601607CF22E005A1E819A0772E111 [localhost_Datafiles2]

state=alive; policy=CLAROpt; priority=0; queued-IOs=0;

Owner: default=SP B, current=SP B       Array failover mode: 4

==============================================================================

--------------- Host ---------------   - Stor -   -- I/O Path --  -- Stats ---

###  HW Path               I/O Paths    Interf.   Mode    State   Q-IOs Errors

==============================================================================

   3 qla2xxx                  sdg       SP A1     active  alive       0      0

   3 qla2xxx                  sdk       SP B1     active  alive       0      0

   4 qla2xxx                  sdq       SP A0     active  alive       0      0

   4 qla2xxx                  sdu       SP B0     active  alive       0      0

Pseudo name=emcpowerg

CLARiiON ID=APMxxxxxxxxxxx [localhost]

Logical device ID=600601607CF22E0084BD035B06CAE211 [localhost_Datafiles3]

state=alive; policy=CLAROpt; priority=0; queued-IOs=0;

Owner: default=SP B, current=SP B       Array failover mode: 4

==============================================================================

--------------- Host ---------------   - Stor -   -- I/O Path --  -- Stats ---

###  HW Path               I/O Paths    Interf.   Mode    State   Q-IOs Errors

==============================================================================

   3 qla2xxx                  sdh       SP A1     active  alive       0      0

   3 qla2xxx                  sdl       SP B1     active  alive       0      0

   4 qla2xxx                  sdr       SP A0     active  alive       0      0

   4 qla2xxx                  sdv       SP B0     active  alive       0      0

Pseudo name=emcpowere

CLARiiON ID=APMxxxxxxxxxxx [localhost]

Logical device ID=600601607CF22E009E434BF0A86FE111 [localhost_Archives]

state=alive; policy=CLAROpt; priority=0; queued-IOs=0;

Owner: default=SP A, current=SP A       Array failover mode: 4

==============================================================================

--------------- Host ---------------   - Stor -   -- I/O Path --  -- Stats ---

###  HW Path               I/O Paths    Interf.   Mode    State   Q-IOs Errors

==============================================================================

   3 qla2xxx                  sdf       SP A1     active  alive       0      0

   3 qla2xxx                  sdj       SP B1     active  alive       0      0

   4 qla2xxx                  sdp       SP A0     active  alive       0      0

   4 qla2xxx                  sdt       SP B0     active  alive       0      0

Pseudo name=emcpowerf

CLARiiON ID=APMxxxxxxxxxxx [localhost]

Logical device ID=600601607CF22E00F86C10EB2172E111 [localhost_Datafiles1]

state=alive; policy=CLAROpt; priority=0; queued-IOs=2;

Owner: default=SP A, current=SP A       Array failover mode: 4

==============================================================================

--------------- Host ---------------   - Stor -   -- I/O Path --  -- Stats ---

###  HW Path               I/O Paths    Interf.   Mode    State   Q-IOs Errors

==============================================================================

   3 qla2xxx                  sde       SP A1     active  alive       1      0

   3 qla2xxx                  sdi       SP B1     active  alive       0      0

   4 qla2xxx              sdo   SP A0 active  alive   0
   4 qla2xxx              sds   SP B0 active  alive   0
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umichklewis
4 Beryllium

Re: EMC PowerPath on Linux and Net-SNMP

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At first glance, it looks like you're using PowerPath with LVM.  emcpowerd is the block (physical) device and emcpowerd1 should be the logical device under LVM control.  Output from 'vgdisplay' should help confirm this.  The I/Os will not quite match, because Linux is sending certain low-level SCSI primitives to the block device and LVM is sending other commands to the logical device.

Let us know if that helps!

Karl

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KyleTucker
1 Copper

Re: EMC PowerPath on Linux and Net-SNMP

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Sorry, yes it is LVM. And pvdisplay shows the "1" devices as the physical volumes.

# pvdisplay | grep emcp

  PV Name               /dev/emcpowerg1

  PV Name               /dev/emcpowerf1

  PV Name               /dev/emcpowere1

  PV Name               /dev/emcpowerd1

So I should only be using the counters from these devices then - not all eight - so my IOPS is actually half what is being picked up by PRTG via Net-SNMP. Is that correct?

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umichklewis
4 Beryllium

Re: EMC PowerPath on Linux and Net-SNMP

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Correct - you'll want to focus on IOPs to devices under LVM control.  Collect the SNMP performance data from those four devices under LVM control.

Let us know if that helps!

Karl

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KyleTucker
1 Copper

Re: EMC PowerPath on Linux and Net-SNMP

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This was very helpful. Thanks so much!