Hi last week I was experimenting a bit with lvm snapshots. What I tried to do was to create 2 snapshots per day from our ~5T "backup" ext3 filesystem which gets rsynced twice a day from the (remote) "real" production filesystem. Our workload changes at most 50G of data a day, so I chose an initial snapshot size of 50G. After each rsync run, the snapshot lvs were extended so that each of them had again 50G free space available. This worked very well for about three days, i.e. six snapshots. From this day on, the system [1] became more and more sluggish during the rsync runs. Hitting return in bash on the otherwise idle system began to take as much as several seconds. Simple lvm commands like lvdisplay took up to several minutes. Two or three days later (i.e. 10+ snapshots) the system froze totally during the rsync. Nothing made it to the system log. I could easily reproduce this by running rsync again or by simply creating a 100M file. Is this an expected behaviour? If so, is there a formula in terms of filesytem/snapshot/ram size to compute the maximal number of snapshots that may be created from the same filesystem without risking to freeze the system? If this behaviour is not expected, what can I do to improve the situation or to debug this problem? Thanks Andre [1] HP Proliant, 2-way AMD Opteron, 5G Ram, linux-2.6.19.x and linux-2.6.20, ubuntu server lvm tools based on libdevmapper-1.02 -- The only person who always got his work done by Friday was Robinson Crusoe
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