Great, thanks for confirming that.  Back to the initial set of messages for a moment:

[May  1 09:23:11.564] Server {0x2afe89312700} WARNING: cache directory overflow on '/dev/sdd' segment 0, purging...
[May  1 09:23:11.565] Server {0x2afe89312700} WARNING: cache directory overflow on '/dev/sdd' segment 0, purging...

This sounds like something it would eventually recover from, but we haven't seen these messages ever stop, once they do.  Can you shine some light on what's happening here?  ATS is functioning properly in this situation, but load increases, and eventually more cache directories get into this state.
 
Sounds like something I should file a bug against?

Thanks for your assistance.

--
Bruce Z. Lysik <blysik@yahoo.com>

From: Leif Hedstrom <zwoop@apache.org>
To: users@trafficserver.apache.org
Cc: Bruce Lysik <blysik@yahoo.com>; John Plevyak <jplevyak@gmail.com>
Sent: Wednesday, May 2, 2012 7:26 AM
Subject: Re: selectively clear device disk cache?

On 5/2/12 7:30 AM, Bruce Lysik wrote:
> Thanks for that suggestion, John.  Objects aren't stored across cache devices, right?  If I clear a single disk cache, it has its own index, and I don't run the risk of putting the ATS server into some weird state, right?
>

Correct. It's a strength, and a weakness. In some cases, a very large, popular file could benefit from spanning multiple disks, but we (currently) don't support that (afaik).

-- leif