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April 19, 2011

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Great blog post, Rob. Explains the vscsi technology very well. Well written.

Yeah - NPIV is great; but make sure your infrastructures meet all the requirements to support NPIV. And check the compatibility matrix docs too. Make sure the versions of the VIO Server and LPAR are support. Good Luck with the NPIV adapter.

I know this thread is a little old, but I wanted to comment about NPIV from a storage admin’s perspective. While you have eluded that NPIV makes things easier on the AIX admins, it shifts that burden to the storage admins. Zoning and masking for NPIV become exponential when compared to vSCSI. Storage admins, depending on the storage platform they support, need to map and track these LUNs in spreadsheet. Things get even more complicated with NPIV and partition mobility due to ‘dark’ WWNs that need to be manually zoned and masked. One big downside of using NPIV is that I can no longer just give a pool of unused LUNs to the VIO and then let the AIX admin assign disk or spin up LPARs as they need them. With NPIV each LPAR is treated as separate hosts, with its own zoning, masking, specifically defined LUNs. I have gone from 4 zones per VIO pair to 4 + 2 for each LPAR.


I agree fully with Ray. Might be a bit old topic but for AIX system admins who do the SAN config as well, it is even more work to use NPIV then using vSCSI. On top of that (as you mentioned briefly) there are dependencies between many LPARs and the connected storage system(s) instead of a few VIOServers and the connected storage systems.


But INDEED NPIV has some strong advantages like:
A) Less spreadsheet management after a Live Partition Mobility (LPM) action ;-)
B) Flash copy kind of commands that must be used and triggered with native storage vendor drivers (not possible with vSCSI).
C) Performanc MIGHT be better. I've not seen any good and valid data about this so far. Just saying..... it is not going through the VIOServer so it is faster is worthless to me


The 3 reasons why you MIGHT consider vSCSI SERIOUSLY:


1) AVAILABILITY
For instance: when using NPIV, a storage vendor might demand to upgrade your storage drivers....... in each LPAR...... cuz of a bug...... meaning rebooting every LPAR that is running with such drivers if it needs an update.

Where as using vSCSI inside a few VIOServers, you can do that on the fly without rebooting your LPARs. Just update one VIOServer and reboot without a hassle that same VIOServer since there is a second VIOServer to take over on the fly (assuming there is a dual VIOServer setup in your frame). Then after the first VIOServer is started succesfully with the new drivers, do the same for the other VIOServer..... on the fly too.


2) ADDITIONAL WORK
Using vSCSI gives you an environment where you use the same native AIX MPIO drivers on all LPARs. No differcences across the board.... all LPARs the same. No additional work INSTALLING drivers native for the storage environment. Where as with NPIV you have to install inside each LPAR the drivers proposed by the vendor.


3) POSSIBLE HIGHER STORAGE LICENSE COSTS
This happens for instance with the DS storage line of IBM. If you are using a DS3500 disk system then you have 4 storage partitions standard. When you have just 2 VIOServers talking to the DS3500 storage then you do not need extra storage partition licenses. Where as using NPIV you have to purchase ADDITIONAL storage partition licenses since each LPAR with NPIV needs his own storage partition (easily surpassing the number of standard storage partitions available on a DS3500).

NPIV is nice but vSCSI is not dead ;-)

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