[ardour-users] Unable to record - 'disk system cannot keep up'

Steven Chamberlain steven at pyro.eu.org
Mon Aug 14 18:57:58 PDT 2006


I've set up 'ardour2' on a new system using 2.6.16-rt29, PAM patched for
rt_prio, latest jackd and ardour2 from SVN.

For some reason I cannot record beyond 10 seconds. For the first five,
everything keeps up and the red/pink areas behind the playcursor are
refreshed with the recorded audio data. At around 5 seconds the red/pink
areas stop updating, and the playback/capture buffers drop down to zero.
About 10 seconds into recording it aborts with the error:
  "The disk system on your computer was not able to keep up with Ardour.
  Specifically, it failed to read data from disk quickly enough to keep
  up with playback."

This happens only when I record 5 or more tracks (up to my maximum of
eight). With 4 tracks or less being recorded, it doesn't stop recording,
just has the occaisional hiccup.

I'm recording at 96kHz to 32-bit WAVE. JACK does not suffer any xruns
while I'm recording (I enabled the option to stop recording if an xrun
happens. I'm saving to an ext3 partition on a (fast?) SCSI RAID when
the rest of the system is idle. The output of
'hdparm -tT /dev/ida/c0d7p1' gives me:
  Timing cached reads:   2776 MB in  2.00 seconds = 1388.39 MB/sec
  Timing buffered disk reads:   94 MB in  3.05 seconds =  30.78 MB/sec

I suspect what may be happening is five seconds' worth of data is being
buffered somewhere, and the disks can't be synced quickly enough to
accept more data. I'm really not sure.

Please can someone suggest why this is happening? I thought my disks
would easily be fast enough to record 5 or more channels at once (this
would be less than 2MBytes/sec, right?)

The system is an Athlon64 X2 (dual-core), 1GB of RAM (and Ardour
succeeds in locking memory), A8N-SLI mobo (nForce4). 'jackd' is getting
realtime priority and only rarely suffers xruns at 128 frames/period, 2
periods/buffer. I also tried with and without POSIX SHM.

Thank you for any help,
Steven Chamberlain
steven at pyro.eu.org

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