[neurosetta] positron experiences and questions

[Dan Berger]

Has anyone out there had any success syncing large (i.e. thousands of
tracks) amounts of music to the Neuros using positron?

I've observed that aside from general usb-storage instability (the
device only wants to be mounted once, though rmmod'ing usb-storage after
unplugging the Neuros and allowing the kernel to re-insert it seems to
help) my system - a 2x1Gz PIII running the latest SMP errata kernel
(2.4.20-18.9smp) from redhat - goes all to cock when running a sync.

I left a positron sync running overnight last night and returned to a
completely hung (not even control-alt-del worked) system this morning.

So this morning I started it up again, and observed that after syncing
about 30 tracks, my system load average started climbing.   It got so
bad that interactive response suffered - the X pointer jumped around
randomly and I realized things were probably going down hill in a
hurry.  

I figured it might be a problem with buffering to or from the USB
storage driver, so I switched to a text VT and typed 'sync'.

A minute later, sync hadn't returned - so I switched to another vt and
did it again.  Still nothing.

I switched to a third vt and ran top - and noticed that positron and
both my sync's were in stat "D" meaning un-interruptible  sleep.

So I killed positron - and within a few minutes the system had returned
- the load average dropped, and I could use X again.

As I started typing this message, I started positron again - and sure
enough - when it hit track 36, the system started seizing up again. 
This time, I killed it (ctrl-c) before I lost X.

Anyone having similar experiences?  Given the long startup-time for
positron (while it scans the sync point), and only being able to sync in
blocks of 30 - it'll take me days to get my 3000 odd tracks copied over.

So, since positron has a rebuild command - I decided to try syncing the
files without positron. 

I fired up rsync

% rsync -rvP --include=\*.ogg --include=\*.mp3 . /mnt/neuros/music

My first observation is that doing file reads off the neuros must be dog
slow - as it's taking rsync forever to decide what files it doesn't need
to update.

My second observation is that writes are pretty slow, too - as rsync
reports about 500kB/s writing files.

My third observation is that after running for 15 minutes, it's still
running any my system is behaving pretty normally.  My load average is
around 2 (vs. 6 or 7 when positron goes haywire) and I can still type
this message (under X).  
 
My fourth observation is that rsync seems to be slowing down as it
writes more data.  Previous tracks were being written (as I said above)
at 500kB/s - the last few have averaged between 90kB/s (!) and 250kB/s.
 
My fifth  and final (at least for now) observation is that during those
times that rsync is getting poor throughput, my load average peaks
around 4 - but once that file is written (and flushed, perhaps?) the
load average drops and rsync continues.

My conclusion is that what seems to be going on is that positron is
aggravating a kernel or usb-storage bug - and that rsync, for whatever
reason, isn't doing the same.

Can anyone out there corroborate these experiences?  Any comment from
the positron folk(s)?


--

...Dan Berger [dberger at oubliette.org]
   http://www.oubliette.org/~dberger
   Inter arma silent leges
   A982 E6B1 CB2F 7A49  843A 9297 DA73 4371  1F54 8D0C

   "Government is not reason. It is not eloquence. It is a force,
    like fire, a dangerous servant and a terrible master."

                                      -- George Washington

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