Sitting at the computer just now, I had one of those "light-bulb" moments of clarity. I have been reading multiple posts about folks that have made recordings where the playback freezes up several minutes into the program, never to be unfrozen, and other effects. I have had the odd similar instance, but certainly not as consistent as these folks (I have had way more successful recordings than aborted ones, including recording two programs simultaneously onto one hard drive). And besides, those symptoms sounded vaguely familiar.......
Finally I remembered. In order to compensate for internal temperature changes, hard drives perform a routine called "thermal recalibration". Here's what Scott Mueller says about it in his reference guide, "Upgrading and Repairing PC's":
"Most hard drives today have sophisticated thermal compensation routines that make adjustments in head position relative to the expanding and contracting platters. Most drives perform this thermal compensation routine once every 5 minutes for the first 30 minutes the drive is running and then every 30 minutes thereafter. In many drives this procedure can be heard as a rapid 'tick-tick-tick-tick' sound."
Data cannot be read from or written to the drive during the one second or more while this routine takes place. On a normal desktop computer it is little more than a fleeting annoyance - kind of like the machine needed to take a breath. But I recalled that this routine was causing nightmares for manufacturers who were trying to record real-time data such as video or audio, and at one time drive manufacturers produced a line of what were called "audio/video" or "A/V" drives which minimized or eliminated the thermal recalibration cycles to allow recording with no perceptible breaks.
A visit to the Seagate site uncovered the following quote:
"Since there is no industry standard for A/V-rated hard drives, there is varying opinion in the computer world about what comprises an A/V hard drive. Generally, the industry consensus for any hard drive to be A/V rated is based on a few factors:
Does the drive feature thermal recalibration? All of the Seagate recent and current SCSI and ATA drives feature an embedded servo that eliminates thermal recalibration, so this is no longer a concern with any of our drives."
Note that Seagate emphasizes that even though their drives used to employ that feature, their current models do not. And they further hint that other manufacturers may have differing standards for this characteristic. Therefore, such drives may still be being marketed.
I have now pretty much convinced myself that the folks that are having regular freezeup problems with their pvr are victims of this hard drive design characteristic. The only way to know for sure is to research the exact model number of the hard drive, which may not be that simple to do (opening up the enclosure, etc.), or ask the drive manufacturer's tech support people. There is no "fix" for it -- a drive which uses this technique is simply not going to record video successfully, even though it might run Windows like a champ.
It has also been brought to my attention that some drives have a built-in "sleep" mode that spins them down after a period of inactivity to conserve power. Although a PVR drive is unlikely to have periods of inactivity (since you are probably using the time-shift feature), it's also worth checking out this possibility as well.
Hard drives in PVR and A/V service
