I was reading the information at:
https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/IBM%20i%20Technology%20Updates/page/IBM%20i%20Functional%20Enhancements%20Details
as reprinted below.
For the purpose of this email thread let's concentrate on the section "SAN
Multipath Support for Tape Drives (IBM i 7.2 TR 2 only)".
Let's say I already have dual VIOS lpars hosting tape for:
- one disk hosting lpar of IBM i
- multiple guest lpar's of IBM i.
- AIX lpar
I looked and apparently we currently only have one of the VIOS lpars
hosting tape for the IBM i lpars while each VIOS lpar does have it's own
physical connection.
Is this what this TR brings to the party? It would allow the multipathing
to allow us to use both VIOS lpars for tape hosting?
And does this mean we would have to exchange our fiber LTO4 drives for
LTO5 or LTO6 to use this capability? Looks that way.
We are using the following:
TS3100/TS3200 (3573)
TS3310 (3576)
<snip>
May 2015 - IBM i 7.2 Technology Refresh 2, IBM i 7.1 Technology Refresh
10
SAN Multipath Support for Tape Drives (IBM i 7.2 TR 2 only)
With IBM® i 7.2 TR 2 and later code levels, support is added to allow most
Fibre Channel tape and tape library devices to be attached multiple times
to the same IBM i partition.
Up to eight paths are supported for each device.
The multipath functions available depend upon the capabilities of the
attached tape and tape library devices.
For maximum redundancy, you can use both ports of the tape devices to
attach to the partition.
Because tape devices are sequential access devices, only one path to
the device can be active at a time.
Attachment may be native to the IBM i partition, or via a VIOS NPIV
configuration, or a mix.
For the newer technology tape and tape library devices, attaching the same
device multiple times to different adapter or adapter ports on the same
the IBM i partition provides a configuration where I/O path failures can
be recovered by vary off and vary on of the affected device descriptions,
or deallocate and allocate of a failing resource within a tape library
device, to switch to an alternative path.
Multipath support with manual fail-over is provided for the following tape
and tape library devices:
Fibre Channel LTO5 and LTO6 drives in the 7226 enclosure
TS3100/TS3200 (3573) with LTO5 and LTO6 Fibre Channel drives
TS3310 (3576) with LTO5 and LTO6 Fibre Channel drives
TS3500/TS4500 with LTO5, LTO6, 3592-E07, and 3592-E08 Fibre Channel
drives
ProtecTIER® virtual tape library, code level 3.3.5.1 or newer
Note: The device driver uses persistent reservation for drives that are
supported with multipath. If a device is attached that emulates a
supported IBM tape drive, but does not support persistent reservation as
expected, the results may be unpredictable.
With this new function, for most of the older technology tape and tape
library devices (not mentioned in the above list of supported drives),
attaching the same device multiple times to a different adapter or adapter
ports on the same IBM i partition provides a usable configuration that
behaves the same as if there was only one path to the device for most
operations, but does not support recovery from path failures.
Multipath tape attachment is not supported at all for the following
devices.
SCSI attached tape devices.
3494 tape library.
</snip>
Rob Berendt
midrange.com
