I have a DS508 with 3x1.5TB Seagates running in RAID5. The install went fine (~6 hrs), copied about 1TB of data over to it, but now when accessing media the system appears to hang for 20-30 seconds at a time every minute or so. Just playing an MP3 is enough to hang it up. The song will keep playing after the 20-30 second pause so it's not a complete failure, when it happens one or two of the drives will flash the activity light about ~5 times a second in unison, not the typical access activity I think, the system looks like it's doing something internally, parity check perhaps, but regardless the logs have nothing pointing to any issue. I'll try to track the problem down and update with any new information.
As far as the data integrity, all the drives spin up without a problem and file access seems to be ok, but I haven't tried copying back a large amount of data to see if it gets hung up in all situations. I can't speak to whether or not a fully loaded DS508 would have any problem, but since the startup amps are on par or less than some of the other "certified" 1TB drives I'm hoping it will be fine. Sadly I couldn't get anymore than 3 of the drives initially. If you have a CS407 or lower model you may want to wait for results with that system. Cheers!
DS508 (Firmware DSM 2.0-0722)
HDDs: 3 x Seagate (ST31500341AS) 1.5TB Drives
Peripherals: Seagate FreeAgent Pro 750GB (USB), APC 550ES Back-UPS (USB)
As far as I can tell the Seagate 1.5TB (ST31500341AS) drives do not function properly with the DS508, at least not under the current (722) firmware. The drives freeze up for ~30-60 seconds every few minutes during even small I/O bursts. I'm not sure if the drives themselves have an issue as a few folks on the web have reported similar behavior outside of the NAS environment (Newegg has a review or two about it). I can't be positive given my limited testing, but I would steer clear of these drives until Synology tests & updates firmware or Seagate updates the drive's firmware if the issue is with the drives. If anyone else has these drives, please post your results. I tried with & without write cache enabled, with and without the 1.5GB/s limit enabled. With the 1.5GB/s jumper enabled the problem did seem to show up less often, but it was still present. I tried creating the array over again as well with the same result. It could be a power issue where the drives don't get the juice they need and subsequently reset the I/O bus or perhaps a bug in the drives themselves. Either way I gave up and put in 3x1TB drives and the NAS now seems stable without any stalls.