Exporting .jpg, and .orf files to .jpg, along with some .mov, and .mpg4. Coming from multiple Lightroom directories to multiple directories for export. Over 50 GB total to over 10 destination directories. Running a reasonably new Windows 7 desktop that is up-to-date. Repeatedly fails if several Exports are started at one time with Windows freezing, no blue or black screen of death, just a full freeze (no mouse, no working reset). Power-down down and restart works OK, but in-flight transfers leave corrupted files on destination (not surprising).
It is possible to start up to 13 parallel Exports, but the hang will happen with as few as 3 running, and maybe only 2. Lightroom source is a pair of 4TB disks mirrored in Windows (not disk controller). Target is an SSD drive (running as C drive). Single Exports work fine.
Looks like a concurrency bug of some kind, maybe in the conversion software to .JPG e.g. the Olympus conversion in Camera Raw, or DNG or TIFF photo formats. Multiple copies using Windows never shows this kind of hard hang on multiple concurrent transfers, nor do other multi-tasked Lightroom operations.
Anyone else seen this problem? Has Adobe recorded this as a known bug?
Running current CC Lightroom.
Many people have reported that LR becomes unusable with multiple exports running. See this report in the official Adobe feedback forum: Lightroom 6 / CC2015: Very slow UI response with background export(s) running. Please add your vote and opinion to that topic.
In LR 5 and earlier, LR did not take advantage of concurrency to do exports -- it did one pic at a time. So people got in the habit of starting multiple exports. But LR 6 / CC 2015 takes advantage of multiple processors and will apply concurrency to a single export, soaking up most available CPU and memory resources. And as many observed, when you start multiple exports, LR doesn't handle it very gracefully.
For people who formerly started multiple exports to get faster throughput for a set of photos to be exported with the same settings, the workaround is simple: Just run one export at a time. But for people who want to queue up many different exports all at once without babysitting their computer for the next hour, LR 6 / CC 2015 is a step backwards.