I'm using partclone to take disk images with this command:
partclone.ntfs -c -s /dev/$mypartition | lzop -c > /my/nfs/share/mypartition.lzo
The partition size is 34.1 GB with 33.8 GB used.
The problem is the performance drops after a while. At first the backup is being written at roughly 300 MB/minute, but the performance gradually drops to 150-200 MB/minute. The estimated time of completion increases from about 1.25 hours to about 2.5 hours.
I took an image with no compression:
partclone.ntfs -c -s /dev/$mypartition -o /my/nfs/share/mypartition
The backup speed hovers around 600 MB/minute, but the performance DOESN'T degrade after a while. It stays around 600 MB/minute more or less.
Is there anything I can do keep the performance from degrading when using compression?
EDIT: I've used gzip and lzop and both suffer from degrading performance. I also tried backing up the same image on a Pentium D machine (2 cores, 3 GB of RAM), and a Xen DomU (1 processor, 512 MB of RAM). They both have the same problem.