I have an Ubuntu 8.04.4 server with an md RAID5 consisting of 9 drives. While transferring a large amount of data to it (through vsftpd) I noticed very bad transfer speed fluctuation.
For example during the transfer of a 20GB archive, every couple of 100MB, the transfer would completely halt for several seconds. Then it would go back up to ~55MB/s. And this would repeat over and over again; leaving me with an overall transfer speed of like 10MB/s.
The server is on the same 1Gb LAN as the machine I am working on, so I assume the LAN is not the problem.
I have observed this behavior on this server several times in the past whenever I have to transfer large data volumes (over 200MB).
Looking at the output of
top or our Cacti graphs did not give me any indication to what might cause this issue.
Any idea on how to diagnose an issue like this would be appreciated.