On Mon 02 Aug 2021 at 13:26:19 (-0400), Stefan Monnier wrote: > Anssi Saari [2021-08-02 19:04:59] wrote: > > David Wright <deb...@lionunicorn.co.uk> writes: > >> On Mon 02 Aug 2021 at 16:14:15 (+0300), Anssi Saari wrote: > >>> Stefan Monnier <monn...@iro.umontreal.ca> writes: > >>> >>> > cp /path/to/file.iso /dev/sdX > >>> >>> dd if=whatever.iso of=/dev/sdX > >>> >> It's up to taste. > >>> > > >>> > Not at all. The only right answer is: > >>> > > >>> > pv -parIe </path/to/file.iso >/dev/sdX > >>> > >>> Actually I'm not sure how good it is to have both -a and -r, pv doesn't > >>> really show which rate counter is which... > >> > >> No need: the rate is far more variable than its average, as time passes. > > > > I guess it depends. Before that comment I tried it on an old USB > > stick. Read speed was pretty much constant if low. So I think it was the > > left rate counter that showed current rate but wouldn't bet on it. > > [ I'm glad my silly intervention brings up a more constructive > discussion ;-) ] > > If they're both pretty much constant, they're presumably both pretty > much equal, so it doesn't matter which is which ;-) > > But indeed, it's not always the case. I'm right now using `pv` to read > data off of a broken drive (a 2TB 2½" drive which apparently has > problems seeking, resulting in a transfer rate of about 45kB/s), and > it's currently showing me 45.0KiB/s and 70.6KiB/s both of which are > quite stable.
Writing "quite stable" cloaks the information nicely. The average can never move away from the rate: a change in the least significant digit gives the game away. > If it weren't for the first sometimes changing to > 44.xKiB/s it'd be hard to know which is which (IIUC the average is > higher because occasionally the drive gives a more reasonable transfer > rate than that measly 45kB/s). So now we're left wondering how you came by this situation. Perhaps you slumped onto the Return key, then woke up after a few minutes, having missed the initial burst that gave rise to the average being more than 50% faster than the current rate. Cheers, David.
