SANcopy: target LUN is larger then source LUN

Question

i have a sancopy session which the target lun is larger then source lun. the source lun is 2T, and the target lun is 2.1T. i want to lun, when sancopy finished, and i mount the target lun back to host, what's the size recognized by host? 2T or 2.1T? thanks a lot.

dynamox · Accepted Answer

actually flare 24 and higher has this functionality

Fast bind
Fast bind is a feature that allows you to allocate and access new LUNs instantly. In current products, the first time any specific disk space is bound into a LUN, it becomes instantly available because the disks are pre-initialized at the factory. The fast bind functionality provides this same nearly instantaneous access to new LUNs for disk space that has been previously used.

dynamox · Answer

2T, it will also display an extra 100G as space available. On windows you can use diskpart to extend into that extra space.

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dynamox · Answer

first ..let me ask you what is it that you are trying to do ? Are you migrating from one array to another ?

dingding1 · Answer

thanks, dynamox. i ask this question because i have VMware host, and VMware ESX don't recognize a raw LUN greater than 2T. my scenario is : the source lun in production system is 2T(formatted as VMFS), i create a san copy session, and the target lun is 2.1T. can you make sure.

also i can make the target lun the same as source, but i'm afraid that the lun init time is long, do you know some option when i bind lun, that i can avoid zero out every bytes in lun? thanks agian.

dingding1 · Answer

yes. i want to migrate lun from a old EMC array to a new EMC array. the hosts(all VMware ESX) are unchanged.

dynamox · Answer

if you can make the target lun the same size, no reason to waste space and introduce confusion. On CX4 binding new LUNs does not take any time (because of fast bind feature). On other arrays if raid group was used previously it will take its time to bind.

dingding1 · Answer

i also agree that it would be 2T. i will test it.

dingding1 · Answer

what is the fast-bind feature, does it still zero out every bytes in the background?

dingding1 · Answer

I'm back. i make a test, and you are right, thanks again.

jupudk · Answer

If I remember correctly, san copy is block level copy and so both the source and target lun should be of the same size.

dynamox · Answer

target can be larger than source, take a look at SanCopy admin guide.

bharath_25 · Answer

Target LUN can be greater then or equal to Source LUN during SANCopy operation.But it shouldn't be less.

VNX

SANcopy: target LUN is larger then source LUN

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