SnapDrive 6.1 Windows with FC RDM LUNs

[john_monahan]

I'm working on an implementation where several SnapManager (SME/SMSQL) products will be running on Windows Virtual Machines.  The ESX servers are all FC connected and I've successfully used SnapDrive to create and connect to RDM LUNs inside the guests.  Since we'll probably end up with 50 or so RDM LUNs when this thing is all said and done, the customer would like to be able to easily identify the RDM LUNs vs the straight VMWare datastore LUNs.  We decided to reserve LUN IDs 0-19 for VMWare datastore formatted LUNs and use 20 and higher for the RDM LUNs.  The problem is when using SnapDrive to connect to a LUN, there is no way I've found to change the LUN ID.  It automatically just picks the next LUN ID available, which throws a wrench into our naming scheme.  What I've been doing instead is creating and attaching the LUN using SnapDrive, then I disconnect and manually remap it on the filer so I can put in my own custom LUN ID.  So I have two questions really.

1.  Does anyone know of a way to tell SnapDrive either a starting LUN ID or provide it a customized LUN ID when connecting to a LUN?

2.  As long as I create and connect the LUN initially using SnapDrive, is there any type of problem with disconnecting it and then doing a manual lun map to that same LUN again?  I just don't know if SnapDrive is doing anything special when it connects and mounts a LUN, different than what a normal Windows server would do with a manual rescan and drive mount.  I thought as long as I initially create the LUN using SnapDrive I'll have the formatting and alignment issues covered, but I'm not sure if I'm missing anything else that would differentate a SnapDrive mounted LUN vs a manually mounted one.

Thanks in advance

[tapesh · Accepted solution]

Hi John,

1. Currently there is no way in SnapDrive to provide customized LUN id when connecting a LUN.

2. I do not see any issue in disconnecting SnapDrive created LUN and map it manually. Only thing you need to take care if you are disconnecting LUN manually , you need to manually delete RDM also. If you are disconnecting LUN using SnapDrive, SnapDrive will delete RDM automatically. So I suggest use SnapDrive to disconnect LUN.

Thanks,

Tapesh.

[umeshv]

Good one Tapesh. I was sure something will be definitely wrong if user does it manually. This will leave stale entry.

Regards,

Umesh B.V.

SDW & SMVI Development, NetApp Bangalore

Direct Line: +91 80.41844272

Mobile: +91.9845014572

[john_monahan]

Thanks for the reply.  Yes I have been using SnapDrive to disconnect the LUN.  One easy step.

[tapesh]

Hi John,

Can you please elaborate on use case why customer require customize LUN ID for RDM LUNs and data store LUNs. How does it will help customer ? So we can try to get some workaround or fix (if possible) in future release.

Thanks,

Tapesh.

[john_monahan]

It is mainly for simplicity purposes/ease of troubleshooting.  They'll probably end up with close to 50 LUNs assigned to a single VMWare farm.  Things will be quite complex.  If they are having problems with LUN 24, then having a standard in place automatically narrows down whether it is a Windows LUN or a VMWare datastore LUN.

[kris_boeckx]

Hi John,

As best practice, you should map your vmware datastores from lun ID 254 and down. RDM's will start at 0 as snapdrive uses the first availaible lun ID when it is connecting a RDM.

Greetings,

Boeckx Kris

Pidpa

[tapesh]

I read that ESX doesn't recognize LUN ID greater than 255 . So I guess better approach would be to keep first few i.e. 50 or 100 for RDM and then start assign for Datastore LUNs. As Kris said correctly SnapDrive assign first available LUN ID when connecting to the LUN.

Thanks,

Tapesh.

[kris_boeckx]

Hi,

When you start at 254 (255?) and then number down (253, 252,...) your VMFS lun ID's, you have no problem.

I don't know if the last lun ID is 255 or 254 ?

Greetings,

Boeckx Kris

Pidpa

[radek_kubka]

255 is the max LUN ID as far as I know (0 is min LUN ID)

[satishv]

The last LUN id is 255.

[john_monahan]

Great idea.  That will make things easy.