On Wed, Aug 01, 2007 at 01:14:40PM -0400, Alan Stern wrote: > On Wed, 1 Aug 2007, Sergey Vlasov wrote: > > > On Tue, Jul 31, 2007 at 11:08:37PM +0100, Kostas Peletidis wrote: > > > Branden Sletteland wrote: > > > > I have also noticed this delay and have through instrumenting code > > > > have found that every block in the device gets read in. I never > > > > checked if it was something in the df, filesystem, SCSI, or USB > > > > subsystems that was causing this. I am usually doing df on USB > > > > storage devices formated as FAT 32 w/ and w/o LBA. > > > > > > > > Branden > > > > > > > > > > > Thanks for your reply Branden. This explains why df would delay for a > > > whole minute to terminate normally with a 500GB usb disk attached and > > > only for a second or two with a 512MB usb stick attached. Btw both are > > > vfat. [...] > > Without "usefree" the vfat code in 2.6.22 will read the whole FAT > > to count free clusters on the filesystem. > > But reading the whole FAT is very different from reading the entire > partition.
Reading the entire 500GB in one minute? I would really like to have such disk :) Most likely "every block" here really means "a large sequential read". Not sure what cluster size would be used for a 500GB FAT32 partition, but with 4KB clusters the FAT size would be about 500MB - reading it over USB could probably take about a minute.
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