since I installed CentOS6 few months ago (kept up-to-date using yum),
I'm facing very poor performances when writing to USB pendrives.
The hardware: a Dell Latitude E6500 laptop (Intel Core Duo P8600
@2.40Ghz), 4Go RAM + 4Go swap, several USB2 pendrives of various brands
(less than old, all formatted as vfat).
When I perform a copy (with cp or midnight commander, copying big AVI
files between 300Mo to 1.4Go) to those devices, whatever the source is
on the same device or on another disk, I notice that the CPU activity
shows 2 phases as far as I can see with the Gnome system monitor applet:
- a phase where both CPUs show less than 20% of activity, and IOWait
is <80%. It lasts the time I would expect such copy to last (say,
it's like writing at 1-4MB/sec to such devices, which is reasonable
- a phase, at least twice as long as 1st phase but this ratio depends
on the file copy size, where CPUs show <5% of activity but IOWait is
During phase 1, system and applications are responsive, as expected
during a file copy to external USB2 disks. During phase 2, system is
slow, applications are often non responsive.
I was not facing this behaviour w/ Fedora 11, not w/ the Windows XP
system also installed on this laptop.
I'm not facing such poor performances when writing to externals SATA
drives (thru the same USB2 ports), even formatted as vfat. Neither when
writing to those pendrives from another hardware system.
`hdparm -tT` is useless here.
I wonder if some mount options aren't wrong with USB pendrives, see:
/dev/sdd1 on /media/monolith type vfat (rw,nosuid,nodev,uhelper=udisks,shortname=mixed,dmask77,utf8=1,flush)
my suspicion is about the flush option, which I find atypical here.
BTW, I'm still unable to control the mount options that are
automatically set by Gnome - even if I can mount manually if I want.
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