Hard Drive Class for Backup Enclosure?

[ottavik]

Does anyone have a recommendation for the class of hard drive to use in a USB attached backup enclosure attached to a NAS unit?
-- WD Red, same as I intend to use in the NAS unit?
-- WD Purple Surveillance drives? these have demand-modulated spin rates and they prioritize writes which seem to be an excellent match for backup operation needs.
-- desktop class drives?

Does the fact that desktop class drives have built in error correction that minimizes the degree to which those errors get reported make them the obvious choice, irrespective of other considerations?

Assuming that NAS backups (generally?) occur during overnight hours, has anyone considered (or actually used) a timer so the backup drive is only on during expected hours of usage, as opposed to spinning continually?

Thanks for the insight.

 

[RMerlin]

I do not recommend Red disks for backups, as the TLER might cause these to be unreliable (i.e. in case of a problem reading a sector, the hard disk will immediately give up instead of retrying).

Over the years I've usually gone with WD Caviar Green for backups. These have now been replaced by WD by the Caviar Blue line.