"Some more info. Oddly, Console messages (search for "ATAPI) do not always correspond to the drive's failure. Sometimes the drive disappears with no error, other times it shows the "device reconfiguration did not complete successfully" error many times without failing. Typically, a second error "Terminating due to unrecoverable Reset error - drive has stopped responding" is definitely fatal.
Either way, I think I've found a solution for the sleepy Pioneer. To stop the drive falling asleep in the first place, I'm using this AppleScript:

repeat
    do shell script "drutil info"
    delay 28
end repeat

So, every 28 seconds, the optical drives are polled. A delay of 120 seconds was too long, but so far so good (a manual sleep and several hours of idling and active use). Hope this script helps someone out; obviously, a Pioneer or Apple firmware fix would be better. I have seen just one of the non-fatal errors after wake from sleep this morning, but the drive is still live.

(Update: After another 09 Mac Pro/BDR-205 user tried that script (saved as app, used as startup item) reported he had to force quit it (when shutting down the system, etc.) Lain later wrote:) That script needed to be force-quit on my system too. However, this alternative script can be happily quit:

on idle
    do shell script "drutil info"
end idle

The default time for idle is 30 seconds, so it does an almost identical job to the first one, but responds to a quit command where the original does not.

---

(Another Update: The above script did not work for one affected reader - here's an alternative script that was later sent (mid-Jan 2010)-Mike

on idle
do shell script "drutil info"
return 28 (return 120 also works - see below)
end idle

Save as an application and check the stay open option.

Update 2: (Jan 21st, 2010) - the reader that sent the above script later wrote:

"The script noted does work, as does one modified by Iain (another one sent in Jan 2010) using "return 120" instead of "return 28". Evidently polling to drive once every 2 minutes is enough to keep it connected.
-David"

---

Given the previous similar issue I had with a Samsung HD, is there perhaps a fussy SATA problem in the Mac Pros? I do have all the hard drive bays filled, though I saw the same behaviour with one older drive removed.
Cheers, Iain."

Several Mac Pro owners with this drive (same drive firmware 1.03) didn't noted any problems (they had system/drive sleep disabled typically) but some have (regardless of settings).
I've got 4 HDs in an 09 Mac Pro (10.6.2, 10.5.8, Vista U, Win7 Pro) and 2 optical drives (OEM LG and prev. model LG BR burner/HD-DVD ROM reader - GGW-H20L, firmware YL05) and have seen no drive sleep problems. Although as I mentoned earlier I always have ES sleep disabled. (I prefer to manually sleep the mac when desired.) But again that's not been a fix for everyone (although I wish I knew why not everyone saw the problem per past reports here.)
The first reader to report this (09 mac pro user) later said disabling sleep _seemed_ to help (hours of use with drive not 'disappearing') but later noted when waking from sleep he saw some of the same console errors. He had OWC exchange it for an LG (and said that seemed fine).

Here's replies from users of other drives:

"While I have not seen the disappearing drive issue with the Pioneer BDR-205, I have seen it with a Samsung non-BluRay drive. I picked up a Samsung SH-S223C 22x DVD drive from an computer store and used a Windows XP partition to update the drive firmware. Several of the Samsung drives can update their firmware via software update from Samsung. Since I had an IDE version of the drive (SH-S222L) in an OWC Firewire/USB case, I burned a DVD consisting of a single 4 GB file. I used the "time cp" command to time how long it takes to copy the file from the DVD to a local hard drive. The IDE DVD burner in the OWC case (connected via USB) worked just fine. The Samsung SH-S223C DVD burner connected via SATA failed. The drive disappears from the Eject menu and the computer had to be rebooted to recover. The error did not occur in the same place for the file (i.e. the file would be 2.7 GB one time and 3.3 GB another time). Serial ATAPI errors:

Dec 13 22:43:20 kernel[0]: SerialATAPI device reconfiguration did not complete successfully. (failedCommandInfo = 0x1)
Dec 13 22:43:39 kernel[0]: SerialATAPI Terminating due to unrecoverable Reset error - drive has stopped responding. (resetType = 0x0, newPowerState = 0x1, failedCommandInfo = 0x1)

About a week ago I ordered a newer Samsung DVD burner (SH-S223L) from Amazon and it worked flawlessly. Later, I purchased one of the OWC Value Line USB enclosures and moved the SH-S223C DVD burner to that case. The copy test works just fine with the drive in that case connected to the Mac Pro via USB. The copy test also worked just fine with the Pioneer BD-205 connected via SATA.
-Steve"

"This is only marginally related but I thought I'd pass it on. I have a MacPro 1,1 (original) 2GHz. 6 months ago I got an LG bluray drive from OWC (H20L), its connected to one of the the "extra" sata ports (ref: Using the Mac Pro's 2 extra onboard SATA Ports) and it always stays asleep after sleeping the mac. Toast 10 will hang if you try to launch it. It is always restored by restarting. Frankly its not something id even try to "fix", i just remember to restart if i need the drive which works fine in all other aspects. Maybe there's a clue here.
-Peter"

For the record I asked what drive firmware version the drive has (I have that same drive in an 09 Mac Pro - no issues like that - drive usable after waking from sleep.)

"About 27-inch iMac Graphics Firmware Update 1.0
Updates the graphics firmware on ATI Radeon HD 4670 and 4850 graphics cards to address issues that may cause image corruption or display flickering.
Do not disturb or shut off the power on your iMac during this update. Loss of power could result in your iMac failing to start up. For detailed information on this update, please visit this website: https://support.apple.com/kb/TS3181
(TS3181 article is no longer online.)
System Requirements: OS X 10.6.2

That Apple TS3181 article was titled iMac (27-inch, Late 2009) display image is corrupted or flickers, which also linked to the firmware updater.
A reader said he applied the firmware update OK and had seen no issues so far, but some other replies noted they'd not seen a problem and/or were waiting to see if others report any problems with the update. I suggested they watch posts in Apple's iMac forum.