On Mon, 2015-07-13 at 15:42 -0600, jd1008 wrote: > > On 07/13/2015 03:13 PM, Patrick O'Callaghan wrote: > > On Mon, 2015-07-13 at 13:50 -0600, jd1008 wrote: > > > I started a tar command from > > > one external eSATA drive (ext4), connected to eSATA port, > > > out to a USB flash drive (with vfat). The USB stick is touted > > > to support 50MB/s write, 160MB/s read. > > Have you actually measured its real write speed for large files? > > Try > > something like: > > > > time dd if=/dev/zero of=/the/usb/drive count=1000 bs=1M > > > > You might be surprised. > > > > poc > As I just replied with the actual read/write performance data > on this USB 3.0 SUperTalentExpress Drive (256GB), I am > much more surprised by the fact that while tarring a large > dir to it from a fast eSATA drive, the system becomes nearly > unusable!!! > So, if this "shtick" is so slow, why is writing to it killing the > response > time for everything else? IIRC USB drives are not DMA driven, i.e. each filesystem block written to the drive has to be pushed over the serial bus and handled by the CPU. Also, check if the drive is mounted with the 'flush' option, which sacrifices speed for greater integrity (i.e. less damage of the user pulls the drive without ejecting it). poc -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines Have a question? Ask away: http://ask.fedoraproject.org
