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I'm trying to copy a 200GB file from an NFS mount to a local disk. The local disk is an XFS filesystem on a LVM on top of a RAID 5 system (hardware RAID controller).
I'm using rsync
to monitor the transfer speed. At the beginning, the IO speed is about 200MB/s, stable for the first 18GB. But then the performance drops by a factor of 10-20 and never recovers to the initial rate. Sometimes it reaches about 50-100MB/s, but just for a few seconds, and then the process seems to hang for a bit.
At the same time all file-stat operations on the target filesystem are blocking for a long time (minutes). Also, interrupting the copy process blocks for several minutes. A subsequent delete of the partly copied file takes also several minutes.
Any ideas what could be causing this?
1looks like you saturated some write disk cache on the local disk. Have you checked the speed if you copy the file local to local with say file bigger than 18GB – jet – 2012-06-05T22:18:54.857