UNIX for Dummies Questions & Answers

hi all,
i'm new here and i have a question,
i wanted to know, what should happen if i delete a LUN that is already mounted on one of my initiators.
thanks!

That depends....

A LUN is looking like a disk from the viewpoint of the client using it. This means, for the client the disk just failed and evaporated into nothingness.

What this means depends on what the client did with the disk: if it used it as a system disk the system probably crashed. If it is an empty disk waiting to be formatted probably nothing happens (the systems configuration may complain somewhat, but this can be repaired online in most cases, a reboot will definitely clear any problem). If the importance of the disk is somewhere in between these two extremes the consequences will probably somewhere in between too.

Again: it depends. tell us more details and you will get more details back.

Just in case you want to be absolved for doing something idiotic ("please tell me that 'rm -rf /' will go unnoticed and will be no problem at all, because i just issued this on our main production database server" - as funny as this may sound, we already had such cases): you can't and we can't.

I hope this helps.

bakunin

It is a LUN that has a FS, there is no constant I/O to it, but should't i except that the System will shout at me?
I see only warning msgs in the dmesg that LUN assignments on the target were changed and SCSI doesn't preform remap...

by the way, rescan-scsi-bus.sh doesn't help - it doesn't remaps the LUN, only reset of the stack does..

Not more so than when a real disk would break. Suppose the LUN would be a physical disk and this disk had just had a headcrash. Your system would (and should!) complain but not stop working at all because of this, no?

Now we are talking. I deduce from this you are using a Linux of some sorts. All the different OSes behave differently and even within Linux there are different HBAs with different behaviors, different drivers with different capabilities, .... You will have to tell a lot more about your environment or you will get answers which are "more or less precise", so to say.

I have only worked with the QLogic HBAs using the Linux-builtin "qla2xxx" module. There is a command ("multipath -<someswitch>" IIRC) to rescan the LUNs attached, but use with care because it will disconnect all the other LUNs for a short time too. If these other LUNs host databases you'd be in for some major recovery in this case.

I hope this helps.

bakunin