Adjusting (RR)Round Robin IOPS limit from default 1000 to 10

Adjusting (RR)Round Robin IOPS limit from default 1000 to 10

Adjusting the limit can provide a positive impact to performance and is recommended by some storage vendors to change IOPS limit to 1

The default of 1000 input/output operations per second (IOPS) sends 1000 I/O down each path before switching. If the load is such that a portion of the 1000 IOPS can saturate the bandwidth of the path, the remaining I/O must wait even if the storage array could service the requests. The IOPS or bytes limit can be adjusted downward allowing the path to be switched at a more frequent rate. The adjustment allows the bandwidth of additional paths to be used while the other path is currently saturated.

To verify current iops limit run : esxcli nmp device list

By default is iops=1000

You see output similar to:

Path Selection Policy: VMW_PSP_RR
Path Selection Policy Device Config: {policy=iops,iops=1000,bytes=10485760,useANO=0;lastPathIndex=1: NumIOsPending=0,numBytesPending=0}
Path Selection Policy Device Custom Config:
Working Paths: vmhba33:C1:T4:L0, vmhba33:C0:T4:L0

If you need to change for 10 or different value follow this instruction:

Step 1 Add new policy

I included additional thing in Step 1 to make sure that the value is automatically correct for all future LUNs that are assigned.
1. check current policy
esxcli storage nmp satp rule list -s VMW_SATP_ALUA

2. Add new policy (I use IBM SVC storage so I run below)
esxcli storage nmp satp rule add -s “VMW_SATP_ALUA” -V “IBM” -M “2145” -P “VMW_PSP_RR” -O “iops=10”
esxcli storage nmp satp rule add -s “VMW_SATP_ALUA” -V “IBM” -M “2810XIV” -P “VMW_PSP_RR” -O “iops=10”

For automation you can use simple script to run on all hosts in your vcenter server

download >> auto_policy_VMW_SATP_ALUA_new

Step 3 Run PowerCLI to implement new value on each existing datastore, RDM, etc

Single host run:

Get-VMhost esx101.vmlab.local| Get-ScsiLun -LunType Disk | Where-Object {$_.MultipathPolicy -like ‘RoundRobin’} | Set-ScsiLun -CommandsToSwitchPath 10

Multiple hosts run:

download >> Lun_iops_changer