Intermittent pauses copying from one usb drive to another
rendaw at zarbosoft.com
Thu Jun 9 06:30:02 UTC 2011
I'm not sure the best way to go about referencing old threads, but I
hope this is acceptable.
I'm having the same issue with two 3.5" drives in USB 2.0 enclosures
operating in USB 1 mode. Like the OP, I see write activity for 1-5
seconds followed by 1-2 minutes of no activity (I get the same vmstat
output). Unlike the OP, I get no error messages in /var/log/messages.
I get the same behavior copying files from a local server both scp'ing
and tar-over-ssh'ing. Doing tcpdump shows the network traffic
completely stop for those pause periods as well (other than some dns or
arp or something chatter every once and a while).
I did try it on a linux box (just because it was handy) and I got full 1
mb/s speeds with dd (dd if=/dev/whatever of=/dev/null). I get around
800kb/s on FreeBSD doing the same test on either drive. I have the two
drives in a ZFS raidz setup, but "top" says I have around 400 of 512mb
ram free and the about 2.0 ghz processor is more or less completely
I tried the same scp to the linux box's internal drive and got no
pausing, so I don't think it's an scp/server issue.
Assuming this isn't caused by drive message incompatibility, is there
some other configuration that could be wrong? Are there some other
diagnostics I could try?
Thank you very much,
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