[pve-devel] [PATCH storage] fix #3004: show progress of offline migration in task log

[Thomas Lamprecht]

Am 14/11/2022 um 13:23 schrieb Leo Nunner:
> On 11/14/22 13:12, Thomas Lamprecht wrote:
>> as unlike a TTY it cannot tell the console to override existing lines, so I
>> guess this will do some periodic printing?
> 
> Yes, as of right now, it prints a new line every second. Maybe one option to make it "prettier"
> would be to limit the lines printed (by, say, only printing every nth line/second), which should
> be rather simple to implement by matching the dd output in Storage.pm, where log lines are
> already being parsed [1].


hmm, once every second is really a bit much; we have lots of users with big
disks but relatively slow throughput, so a duration of a few hours is
realistic, a poor sole may even need to wait for over a day (sending 4 TB with
50 MB/s need almost a day), which would then produce about 8.64 MB of progress
information in the task log (assuming 100 bytes per round).

What I always like for such things is to reduce report frequency with time,
that way you provide good value/cost ratio w.r.t. reporting for both ends of
the duration spectrum.

E.g., start out with once every 3s, then after a minute (20 rounds) cool the
frequency off to once every 10s, then after a total of ten minutes reduce
further to once every 30s and keep it at that. Compared to the straight 1 Hz
variant, which required ~8.64 MB, we would only need 293 KB. almost 30 times
less storage.