Are there any drawbacks of running Caviar Red (or any other NAS-ready) HDD on your desktop PC?

Short answer:

You can use a WD red without problem as a desktop drive, though they tend to be a bit more expensive.

Longer answer with background:

As long as you are limiting yourself to WD, you got these choices:

• WD Blue: Regular drives. WD standard.
• WD Black: Performance version. Usually faster but drawing more power and generating more heat.
• WD Green: Eco version. Usually slower due to lower RPM. Idle/power down value set to go to sleep mode after a short while.
• WD purple: These are drives optimised for writing and relative low power. Their typical usage would be 24/7 recording of security video.
• WD Red: Same as the normal drives, but with TLER set. (Possibly also better tested, though that might be marketing).

TLER explanation:

When a drive reads a sectors it does not only read the data, but also header and a checksum. If these is an error then the drive will try to read the sector again. Just how often it will try that depends on the drive and the firmware.

In a regular consumer drive two things can happen:

1. A value in a register gets increased. (You can check that via S.M.A.R.T.).
2. Or the physical sector is no longer trusted. The drive will re-read the data until succeeds and then write it to a spare sector. The next time this data is accessed it will be read from that spare sector.
   (Assuming the drive is not out of spare sectors).

This is fine behaviour for consumer drives. However it can lead to problem in a RAID array when it takes a long time to successfully read the sector. If that takes too long the RAID array will consider the whole drive faulty and will drop it. To prevent that you can set a time limited error recovery (TLER), usually to 7 or 12 seconds. If the drive can not successfully deal with a bad sector within that time it will return a read error and continue.

Enterprise level drives are usually shipped with TLER enabled. Consumer drivers are not. WD reds are consumer SATA drives which do ship with TLER and which should be tested to run 24/7 for a few years. This does not prevent you from using them in a desktop.