Pre established RAID runs very slowly

[pioneerx01]

I have a external hardware RAID enclosure (SANS DIGITAL TR4UTBPN) with 4x 3TB Seagates (sad for me) in RAID 5 set-up connected via eSATA with 6.6TB (81%) in data. I had this set-up for several years and it was running fine until yesterday; when transfer rates dropped like a rock. There were no updates or changes done on the PC or the enclosure. It took me 5min to transfer out 1GB of data, where transfer works for few seconds then stops and resumes. When watching something the video plays for few seconds, freezes, them plays and it just repeats. It is like watching an HD movie on PC that is too old for HD movies.

I connected the enclosure to other PC and tried the USB as well, but same issues. The raid utility provided by Sans Digital shows the raid to be all OK with no issues.

I don't know what to do, the raid is essentially unusable due to slow speeds. Any help would be appreciated. Thanks

 

[pioneerx01]

OK, so I started to do a little creative and alternate diagnosis. Since the RAID was behaving like an old drive about to fail, I have assumed that one was in such state, even though Sans Digital Raid Utility states they are all OK, shame shame. I started to pull out one drive out of the array at a time and testing its performance. When I removed out the second drive, the raid was back to its formal glory. So the drive 2 was causing the issues. Independent testing determined that it failed SMART check.

 

[LNCPapa]

Don't leave that array in degraded mode for long.

 

[pioneerx01]

Oh no. It is completely off awaiting new drive. All the drives were purchased at the same time, so there is a chance another one may be on its way out soon, so no I am not "raiding" without a net