Dear Steve,

  Thank you for your quick response.

> I suspect the COPY is failing at some point and then restarting.

  You are quite right!   COPY is failing our large table and then restarting:

2011-02-13 03:23:38 PSTERROR  remoteWorkerThread_1: copy from stdin on
local node - PGRES_FATAL_ERROR ERROR:  could not extend relation
base/25219965/26699570: No space left on device

2011-02-13 03:23:38 PSTWARN   remoteWorkerThread_1: data copy for set
1 failed 1 times - sleep 15 seconds

...

2011-02-13 11:01:47 PSTERROR  remoteWorkerThread_1: copy from stdin on
local node - PGRES_FATAL_ERROR ERROR:  could not extend relation
base/25219965/27037006: wrote only 4096 of 8192 bytes at block 136871

2011-02-13 11:01:47 PSTWARN   remoteWorkerThread_1: data copy for set
1 failed 6 times - sleep 60 seconds


> As to your disk space issue, do you know which tables are using the space?
>

On the master database, yes.  But on the slave my db size is reported
(by "psql -c '\l+'  ") as 19 MB!


I tried this:
Shut down the Slon slave.  (Disk usage still near 100%. )
Shut down Postgres server.  (Disk usage dropped to 7%. )
Started Postgres.  Started Slon Slave.  The copy of the replication
set resumed.
Let's see how it goes now.


Best,
Aleksey