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December 19th, 2014 03:00
Celerra NS40G Storage Pool, with FC disks at the backend (CX4-80)
Hiya,
Some time ago, a storage pool was created on our Celerra NAS head unit, and all the disks that were assigned to it were Fibre Channel 15K drives (at the san side), using Raid Groups.
This has been seen as overkill and we would like to move the data onto SATA Drives so as to free up FC disks for our apps that require high I/O.
Can i simply perform LUN Migrations of the disks on the back end of the NAS (In the Clariion)? I was told there is some kind of rule that prevenets SATA LUNS and FC lLUNS being mixed within a Celerra Storage Pool.
If this is true, then Storage Tiering with Storage Pools must also be prohibited, for Celerra LUNs, as the data will move between the different types of drives.
Im wondering if anyone has experience of this kind of thing, or aware of any white papers that would show conclusivley this to be the case?
I find it hard to accept that a Celerra NAS is sensitive enough that you cannot mix the back-end LUN types. Normally a host would be oblivious as to the makup of the disks?
Thanks,
Dave
Rainer_EMC
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December 19th, 2014 06:00
Hi,
it depends on which disk type the data mover has classified the LUN.
For auto-tiered LUNs we just see this as MIXED – for LUNs from one tier or classic LUNs we use different disk types.
Among other stuff the disk type is used by AVM to decide which LUNs are used to extend a file system.
More details are in the AVM and MVM manuals.
You should only use LUN migration for NAS LUNs if src and dst have the same disk type.
If you don’t adhere to this then it can happen that the dst has the wrong disk type and AVM operations don’t work correctly.
Otherwise you can use Replicator or client based migration.