Been running a snapmirror / snapvault cascade in my environment for years since 7-mode. (Primary --> snapmirrored Secondary --> SnapVaulted Tertiary).
When we were on 7-mode, I was able to enable deduplication on the primary (and thus the secondary), and seperately enable compression on the tertiary. This used to yield good space savings.
Now that we're on CDOT 8.2.2, I'd like to enable compression on the tertiary, but after reading this, I'm not so sure:
"If the secondary volume has additional compression enabled, storage efficiency is not preserved. Storage efficiency on all data transfers in SnapVault relationships is not preserved when the secondary volume has additional compression enabled. Because of the loss of storage efficiency, a warning message is displayed when you enable compression on a SnapVault secondary volume. After you enable compression on the secondary volume, you can never have storage-efficient transfers."
There is no mention of tertiary volumes and compression on CDOT that I can find.
On the System Manager gui, the tertiary volume only offers the ability to enable storage efficiency (not checked by default) or not.
Try to enable compression on the tertiary volume via command line and I get this stern warning:
::> volume efficiency modify -vserver vservername -volume tertiaryvolume -compression true
Warning: Enabling compression on a secondary volume is strongly discouraged. If compression is enabled on a secondary volume, storage efficiency present on the source will not be
preserved during replication. The destination system needs to run offline storage efficiency scanner (compression and dedupe) to achieve storage savings. Additional
compression savings on the destination comes at a cost of extra computation resources. In environments where there is a lot of shared data present on the source, (e.g.,
virtualized environments employing file clones), data inflation during transfer may lead to failed backups due to lack of space on the secondary volume.
So compression is not an option on a snapvault tertiary volume? Anyone tried this on a CDOT system?
