Ignite-UX and SAS white paper

9
What you can do with SAS devices
You can replace SAS devices that have failed. You should, however, consult the SAS
documentation and documentation for the revision of HP-UX you are running for the correct
procedure for replacing SAS devices. Simply replacing a device while the system is up will create a
new hardware path for the device (since it does not have the same WWN as the original device).
To complete the replacement of a SAS device while the system is running you must use the
sasmgr(1m) command’s replace_tgt option. On 11i v3 you will need to run
io_redirect_dsf(1m) to have the new device use the persistent DSF of the device it has
replaced. Failing to do this can lead to recovery problems because of hardware path changes.
Replacing the device while performing a recovery or cold install will work as expected since any
mapping between WWN and hardware path is preserved with the Device Specifier (see the
instl_adm(4) section Device Specifier for more details).
You can remove SAS devices in order of highest bay downwards without affecting how your
system will be recovered. Note that importing any LVM volume group that was on the SAS devices
that have been removed will fail for recovery archives created before the devices were removed. If
you subsequently add new SAS devices back, you should consult the SAS documentation and
documentation for the release of HP-UX you are running to determine if any additional
configuration steps are required.
You can add new SAS devices but you should not leave any empty bays between new SAS
devices. You might need to perform the steps required for replacing a device; consult the SAS
documentation and documentation the release of HP-UX you are running for more information. If
you are unsure of the numbering of SAS bays, always consult hardware documentation before
adding a SAS device into an enclosure to determine the next available SAS bay. On an rx6600 if
you have the bays loaded from Bay 8 downwards, you can add SAS devices into Bay 9 onwards
if they are not already occupied.