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Author Topic: Mysterious short pause during playback Frank Cox Film God Posts: 2234 From: Melville Saskatchewan Canada Registered: Apr 2011 posted 04-19-2012 06:38 PM                        Here is something I haven't seen before. I have a GDC server and a Christie projector. I'm playing Titanic 3d tomorrow night so I was doing my QC screening of it this afternoon. Just about exactly one hour in (during the dinner party scene) the picture and sound froze. As soon as I got over my surprise I zipped up to the projection room. By the time I got there (maybe one minute later), it was playing again just like nothing happened. No error messages on the server display, either. I paused the playback and backed up to just before the start of the dinner party scene and started playing it from there. No problem, no pause, from there right through to the end of the movie. When the credits were running I paused it again and backed up to just before the start of the dinner party again and played through that scene again. No pause, no problem. So... what happened there and should I be worried? Seems ok now and there were no error messages anywhere that I saw.  |  IP: Logged Justin Hamaker Film God Posts: 2253 From: Lakeport, CA USA Registered: Jan 2004 posted 04-19-2012 06:51 PM                        I would suspect some sort of processing issue on the GDC which cause the hang - perhaps a file finished ingesting or something similar. If the just the picture paused and the sound continued uninterrupted, then there was probably some kind of data bottleneck in the projector.  |  IP: Logged Frank Cox Film God Posts: 2234 From: Melville Saskatchewan Canada Registered: Apr 2011 posted 04-19-2012 07:08 PM                        Both the picture and sound froze, as though the movie went on pause. I still had a picture, but it stopped moving. No sound at all while it was stopped. Absolutely nothing else was going on, other than playing the movie. My server and projector are stand-alone, they aren't hooked up to anything other than themselves. I checked the server status screen and it reports OK for everything that's listed there.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 04-19-2012 07:52 PM                     Seen it happen a lot on GDCs. I think that is called a "feature". I've never been able to get a straight answer, but if anyone here knows of a fix, please do share.  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 04-20-2012 06:55 AM                     It's your intermission  |  IP: Logged Rick Raskin Phenomenal Film Handler Posts: 1100 From: Manassas Virginia Registered: Jan 2003 posted 04-20-2012 07:45 AM                     I am not familiar with the architecture of these servers but from my experience with broadband data networks, I would suspect that there is a buffering issue in the GDC. I did see a similar issue where resizing the buffer solved the problem. In another instance the scheduling algorithm needed tweaking. In either case I think the problem is with the undocumented "feature" of the GDC. Of course, the real test here is does the problem reoccur?  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 04-20-2012 09:41 AM                        Bad disk in the array or a RAID controller issue, perhaps?  |  IP: Logged Frank Cox Film God Posts: 2234 From: Melville Saskatchewan Canada Registered: Apr 2011 posted 04-20-2012 12:32 PM                        I would think that if it was a disk or disk controller board issue that would be reported as an error on the status screen. In fact, a disk error was my first thought when it happened. But there are no errors reported that I can see. I had no issues with the two (different) movies that I played last night, and we'll see what happens with Titanic tonight. Needless to say, I'll be babysitting the projector during the dinner party scene.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 04-20-2012 02:09 PM                     quote: Scott Norwood Bad disk in the array or a RAID controller issue, perhaps? FYI: 3 drive raid5 and the raid is software, not hardware.  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 04-20-2012 02:15 PM                        Wow. Software RAID 5 is not safe. A power failure during a write operation will probably kill the filesystem. The only way to do RAID 5 safely is with a controller with a battery backup on board (they usually use little button batteries like motherboards use for CMOS). Also, RAID 5 implemented in software has some significant performance penalties in write operations, although it should be a nonissue for reads. Software RAID is fine for striping and mirroring (RAID 0 and RAID 1, respectively), but not really a good idea for RAID 5, RAID 6, etc.  |  IP: Logged Jason Raftery Film Handler Posts: 72 From: San Diego, CA, USA Registered: May 2011 posted 04-20-2012 02:28 PM                     Perhaps the array encountered an unrecoverable data block during playback and that was what caused the brief interruption? I've seen this happen once on a Dolby DSS100/DSP100 where playback briefly stalled before continuing as if nothing had happened. A check of the number of bad data blocks recorded by the server on each drive showed that one of the drives recorded a new bad block during the show. Do GDC's servers record a similar metric?  |  IP: Logged Frank Cox Film God Posts: 2234 From: Melville Saskatchewan Canada Registered: Apr 2011 posted 04-21-2012 12:42 AM                        Tonight's show went off without any problem or pause. So I guess that was a one-time glitch. Hopefully it doesn't decide to return.  |  IP: Logged Terrence Meiczinger Film Handler Posts: 45 From: Orono, Me, USA Registered: Dec 2008 posted 04-21-2012 12:58 AM                        quote: Scott Norwood Wow. Software RAID 5 is not safe. A power failure during a write operation will probably kill the filesystem. No, it really shouldn't. Most software raid implementations catalog data that they claim to have written into parity. After a power failure the drives should resync (not rebuild) next time they boot to ensure everything is correct. The issue would be if a drive failed prior to the resync. However, even in a hardware raid this could be an issue depending on the RAID type and which drive failed. As far as performance, it's hard to say as it depends on a few variables, CPU, drives, number of reads/writes, data chunks, etc. In a degraded state, software raid could take a bigger hit. I've even seen software RAID outperform cheap hardware controllers. RAID is not a backup solution. It's a redundancy solution.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 04-21-2012 04:01 PM                     Question: do you power cycle (cold boot) your servers once a week to rid of "stale" memory? How full are the drives, for possible that when the drives are getting above a certain percentage, access from the drives could be a bit troublesome, but don't know about the GDC setup. I usually maintain drive space to be less than 70% at all times.  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 04-21-2012 04:56 PM                     Hi Scott, Interesting, I did not know. But how can the HW RAID controller complete the writing process if the drives are shutting down as well?  |  IP: Logged

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