Just swifted from EMC VNX, wondering if to create multple luns from same volume is a good practice. it will be easier for us to take snapshot on multiple luns. i didn't see snapshot consistency group on system manager, not sure if it is only avaialbe on command line or snapcenter.
Yes, you can without any issues. As you may be aware, NetApp runs on ONTAP with WAFL as it's filesystem, snapshots happens at VOLUME level, so whether consistent or not there wil be a single snapshot for all LUNs contained inside it.
As the LUNs are hosted and formatted by the front end OS, the consistency is ensured by SnapManagers/SnapCenter product on the host side. SnapCenter groups multiple LUNs in a resource group and co-ordinates betwen application and storage to make sure they are applicant consistent when the backup is triggered.
Pros: Multiple LUNs on single volume 1) De-duplication happens at the volume level, so if you have multiple luns with similar data type then you will save more space savings. 2) Snapshot happens at the volume level, so just one snapshot is enough to create a consistent data-set. 3) Space Utilization :The space utilization is dependent on the number of snapshots created and the retention period defined for the snapshots.
Therefore some planing based on the data-rate change is useful: Group LUNs according to their rate of change. For example, group LUNs with a high rate of change in the same volume and group LUNs with a low rate of change in a separate volume.
Nice to know : In WAFL, there is no performance penalty for creating Snapshot copies because data is never moved as it is with other copy-out technologies. However, the cost for Snapshot copies is directly propotional to rate of block-level changes. Hence, having separate volumes for LUNs(apps) having high rate of change is a good practice, so the snapshots can be scheduled more often comapred to LUns that have low rate of cahnge.
Cons: 1) single-file/lun restore can be slow, rather having a single lun in a sinlge volume, allows you to do volume level restore quickly. 2) Requires monitoring volume space as it can cuase offlining all luns; but with auto-grow and auto-delete features this can be tackeld.