WD Red falls from RAID

[RomaL]

Hello,

 I built RAID5 made of two Hitachi Deskstar and two recently purchased WD Red 3Tb HDDs (to work with Adaptec 3805).  It worked for a week and then one of the Reds had disappeared from the RAID. I thought it was cable and changed it with another one. The disk stayed in RAID for some minutes and then disappeared again. It needs power off-on to reappear in RAID in a degraded state. Give me please your thoughts what might be the reason for such an inappropriate behavior for a drive widely promoted as “NAS-oriented”?

thank you!

upd: the similar problem:  http://superuser.com/questions/469060/hdds-randomly-falling-off-raid/506425#506425

[Wizer]

Remove from the RAID and run a diagnostic test

bad drive might need to be replaced

[RomaL]

Thank you for quick response. What kind of testing you think I should execute? Will wd diagnostic tool be enough?

[Wizer]

yup

you can also try HD Tune and chkdsk