WD1501FASS RAID 1 support?

I helped a friend build an awesome computer.  He opted for a RAID set up using the onboard controller, and we bought four of these drives.  My bad, didn’t know that they wouldn’t work in RAID 10, as they do not have TLER.  (Learned this the hard way, from a drive dropping out).  So I (re)built the drives as two RAID 1, which these drives are listed as supporting (provided you are not using an enterprise HBA – which I’m not, I’m using the onboard chip on my ASUS P6X58-E WS).

Here’s the trouble.  About a day after setting up the RAID 1 arrays, one of the disks falls out of one of the RAID 1 arrays.  I told my friend to “mark drive as normal” and I will look in to this as the rebuild happens.

So my question are :  

->  In a desktop/consumer RAID 1 setup, what kind of reliability can be expected?  

->  If it fails on day one, is this going to keep happening?  

->  Have I done something wrong, and if so, can I fix it?

Thanks for any help.

I see conflicting information in these forums…

According to Bill_S, Community Manager on 

06-25-2010 05:21 PM - last edited on 06-25-2010 05:24 PM

Re: WD1001FALS-00E8B0 any problems with RAID?

"Those drives are not designed, nor recommended, for RAID useage.  Because of the error checking utility in the firmware, they could fall out of RAID at any time. 

And, there is no way for you to activate TLER in them, either, in order to make them RAID compatible."

Albeit, he was answering a question regarding a system with both RAID 5 and RAID 1, but he seems to be making a blanket statement for all RAID.  This is confusing because the product specs from WD states that RAID 0 & RAID 1 are supported with a non-enterprise HBA.


I really need to know if I am going to be able to use these drives in RAID 1 with any usable reliability.

What I said back in June 2010 has changed.  These drives have now been recommended by our product people for use in home RAID 0 and RAID 1 applications.  They are not recommended in Enterprise type situations, which means that they are not designed for 24/7 usage.  If you are intending to run the computer 24 hours a day, then you may have problems with the drives dropping out of RAID.  And they definitely won’t work in a RAID 10, but they should work in RAID 1. 

I thought there was an update or software that would disable TLER…

Plan B: use it as a regular single drive and run fill/incremental backups onto the second one.  Iike that setup better since it provides hardware fault tolerance that RAID1 does (albeit less convenient) but also file/user-error fault tolerance by having a system image + backup archives over time.

RoloX2 wrote:

I thought there was an update or software that would disable TLER…


not anymore.  wd won’t put it out. besides, he needs tler turned on for the raid environment.