This behavior is symptomatic of memory fragmentation. When reads are faster than writes, system buffers get filled up, memory fragmentation gets worse, and things can drag to a crawl. Check fragmentation by cat /proc/buddyinfo and see the situation. Manual attempts to change the dirty bytes/ratio for a fix may help certain situations, but slowing down the data passing to the buffers by requesting a hugh amount may be enough to force the defrag to provide the user requested buffersize. for tar use the --record-size=500M to force the defrag to trigger. Of course, it also helps to reduce buffer use with nocache on the copy command and to turn off daemons caching things like .img files (virt- manager has such a daemon). The copy rate I saw copying a 300GB partition to a USB3 mounted SSD with just nocache and record-size=500M on a tar command was 200MB/sec (16 GB memory). Same machine without mitigations has show rates of 10MB/sec on copying a 60GB file.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2095292 Title: rsync to usb ssd blocked for more than 122 seconds To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-signed-hwe-6.8/+bug/2095292/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
