VIO Disk Tuning

I setup VIO servers so rarely, that it’s really easy to miss a step. These are some of the tuning commands I use when setting up VIO. Set these on the VIO server.

Set the FC adapter error recovery policy to fast_fail:

chdev -dev fscsi0 -attr fc_err_recov=fast_fail -perm

Enable dynamic tracking on the FC adapter:

chdev -dev fscsi0 -attr dyntrk=yes -perm

Set the FC adapter link type to point-to-point:

chdev -dev fcs0 -attr init_link=pt2pt -perm

I haven’t found a need to tweak the num_cmd_elems, lg_term_dma, or max_xfer_size with 4Gb Fibre Channel.
For each disk to be used as a VTD, disable SCSI reservations:

chdev -dev hdisk1 -attr reserve_policy=no_reserve -perm

After these are run, reboot the VIO server. And then check these on the client LPARs.

Set the VSCSI error recovery mode to fast_fail for each VSCSI adapter:

chdev -l vscsi0 -a vscsi_err_recov=fast_fail

Set the VSCSI path timeout for each VSCSI adapter:

chdev -l vscsi0 -a vscsi_path_to=30

Set the healthcheck mode and interval:

chdev -l hdisk0 -a hcheck_mode=nonactive -a hcheck_interval=20


    Chris Gibson

    And this….in a dual VIOS MPIO environment.

    # chdev -l vscsi0 -a vscsi_err_recov=fast_fail
    # chdev -l vscsi1 -a vscsi_err_recov=fast_fail

      Pat Vaughan

      I haven’t set fast_fail on my VIO clients. fast_fail for the client vscsi adapters isn’t in the IBM Training books as of 2010. I asked an IBM resource about it and got a “you can try it” answer. Looks like this requires VIOS 2.1 and AIX 5.3 TL9 or AIX 6.1 TL2. In my experience MPIO works fine without it, never had an issue, though in testing turning it on didn’t cause any problems. Thanks for the pointer.

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