2011-08-12 04:24 PM
I have a couple questions about quiescing a snapmirror relationship.
1. Do quiesce commands run sequentially or parallel?
2. If parallel, how many processes at a time?
3. Once a quiesce command is issued is the process noted in /etc/log/snapmirror?
4. The volume requires 5% free space does the aggr require the same?
5. Is there any way to determine how long the quiesce process will take to complete?
2011-08-15 12:09 AM
I am pretty sure you can quiesce multiple SnapMirror relationships at the same time. The number would be dependent on your storage controllers (Check out the 'Data ONTAP Data Protection Online Backup and Recovery Guide' some good SnapMirror info in there)
From memory a quiesce operation is logged to the SnapMirror log file but it has been a while since I ran the command so someone else will have to confirm that one.
It is difficult to determine how long it would take to quiesce a relationship, it would depend on how much data needs to be compared/quiesced and how quick your links between the controllers are. For us a quiesce is usually pretty quick (less than a minute) but we have fast links (10Gbps) between our sites and not a low rate of change on our data.
I am not sure if there is a specific aggregate value for free space when quiescing a volume per se, but you should always keep some free space in your aggregate. This is particularly important for Data ONTAP upgrades, aggregate snapshots (if you have removed your aggregate snap reserve) and general WAFL maintenance (including WAFL reallocates and the like.) I like to keep at least 10% free in our aggregates just to be on the safe side.