On Sat, Aug 29, 2009 at 10:22 PM, Patrick O'Callaghan <[email protected] > wrote:
> Just a quick note to call people's attention to > > http://marc-abramowitz.com/archives/2007/02/17/getting-good-performance-out-of-usb-hard-drives-in-linux/. > This is a couple of years old but it worked like a charm for me. > > Briefly, there's a kernel parameter > called /sys/block/sd[a,b,...]/device/max_sectors (for USB drives sda, > sdb etc.). This specifies the maximum size of a disk I/O operation for > USB storage devices in units of 512 bytes, the default value being 240, > i.e. 120KB (see http://www.linux-usb.org/FAQ.html#i5). The max_sectors > value can be changed doing "echo N > ..." as root, and can have a > dramatic effect on write performance for USB devices such as pendrives. > > I tested this by writing over 2GB to a fresh VFAT filesystem on a 4GB > Kingston Data Traveller pendrive plugged into a USB2 port with the EHCI > driver (as indicated by dmesg). With the default setting, this took > nearly 90 minutes including a final sync to flush the buffers. Using a > max_sectors value of 1024 -- the highest the system would accept -- the > time was reduced to under 16 minutes, a better than 5 times speedup. > YMMV of course, as different brands of pendrive can have very different > performance characteristics. > > Note that the value resets to the default when you unplug the drive, so > you need to set it manually each time. I don't know if there's a way to > do this automatically, or change the default value > permanently.<http://fedoraproject.org/wiki/Communicate/MailingListGuidelines> > There are probably other ways, but you could create a udev rule to run a shell script to set the value each time your particular device was plugged: http://reactivated.net/writing_udev_rules.html#external-run HTH, -- -jp If you want to be the most popular person in your class, whenever the professor pauses in his lecture, just let out a big snort and say "How do you figger that!" real loud. Then lean back and sort of smirk. deepthoughtsbyjackhandey.com
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