Discussing all things virtualization and storage in the data center.

LUN (or data) migration.

I read the Cisco DMM literature and wished even more that I had a SSM somewhere in my SAN.  I see all the other posts comparing oranges with apples (EMC versus HDS) but never see much when it comes to switches.  Sure enough Brocade introduced the DDM a few months before Cisco introduced DMM.  I suppose I am a HDS bigot but you can mulitply that by a million times when it comes to switches.  Hopefully Cisco will pay me something to say how much I like them so I can keep in line with previous blogs....

Anyway, the reason for this posting is my frustration with HDS when it comes to moving data around inside the system.  Hopefully someone can point out that it can be done and that would make my day but I don't think its possible.  Almost every migration that I know of in the USP is done with same to same.  That is same emulation type and exactly the same size at the LDEV level (block level). 

What I have are a number of largish LUSE LUNs that need to be moved to concatenated parity groups.  Eg, lets say I have a LUSE made up of 16 x 39 GB LDEV's (624 GB).  HDS suggest that the max number of LUN's in a LUSE should be six.  So I could make a 6 x 104 GB LUSE in the concat parity group.  But how can I move the data from the original to the new LUSE?  I just don't know of anything that will do it in the USP. 

This is where the Cisco DMM or Brocade DDM comes in.  Cisco says you can do the migration without any downtime but I serious doubt that can be achieved.  Brocade talk about one host reboot.  At least the switch offers something of an option to do this migration.

I know of a number of ways of moving data at the host level (eg Robocopy or Veritas Mirroring) but I would really appreciate the ability to move data to non same LDEVs' at the storage level and having this done without any apparent disruption.

Considering HDS's constant push of Tiered Storage Manager, I am a bit surprised that same to same size is still enforced.

So, have I missed something here?  Can data be migrated inside the USP (including virtualised data) the way I want it done?  HDS sort of whispered something about using True Copy or Shadow Image to do that but again, it seems to be same size to same size.

Do the storage vendors (at least HDS) need to address this requirement or are they satisfied with leaving it up to switch vendors to do it in the fabric?


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