So Im 26 hours into a preclear of a 6TB WD Red and I have just realised that my electric is going to be shut off in 8 hours time for approximately 2 hours. I know I can cancel the preclear at anytime but as its at 2% through the post read at the moment I would estimate based on my last 6TB preclear that it will finish in 53 hours total so I will cancel it in the morning and it will be at approximately 37% post read. I only ever do one preclear cycle normally. What Im wondering is do you think I should do another preclear cycle after the electric comes on or just add it to the array as it will have a preclear signature written to the drive. I have had no errors on the drive so far.

Me personally, I would preclear it two more times.  I do three.  Yes it takes longer, but I want to return and get a new drive if anything is wrong versus a possible refurbished unit.

 

At a minimum, I would want at least one complete preclear.

The preclear script has switches that let you modify its behavior. You can restart it and have it only do the post-read, for example. If you run it without any parameters it will display its help. Here are some excerpts from that help that might be of interest to you in this situation:

 

To test if a drive is cleared:

      ./preclear_disk.sh -t /dev/???

To run the post-read-verify only on a drive.

      ./preclear_disk.sh -V [-A|-a] /dev/???

You can skip the optional [-A/-a] switch in that one. It is only needed to override the default partition start and has no effect on drives >2.2GB anyway.

Maybe Joe will comment here, but I don't think it's a safe assumption that the drive already has a valid preclear signature at this point. If I were you, I'd just do a shortened preclear after the power comes back, or use the command line switches to verify if the drive does indeed have a valid preclear signature ( -t ) and if it doesn't, just do a short preclear with the -n switch.

 

I'm not sure if the post read verify option actually writes the preclear signature or not.

Thanks Guys, I will just run the post read that trurl mentioned preclear_disk.sh -V /dev/sdX

Thanks Guys, I will just run the post read that trurl mentioned preclear_disk.sh -V /dev/sdX

Make sure you do the test with the -t option before you try to assign it to make sure the preclear signature is intact.

I did that before the post testing, I new it should be as JoeL mentioned it in one of the preclear forum posts that it writes the signature to the disk after it has zeroed it out. But thanks. It looks like it will be 53 hours for a complete preclear on this disk as well. I was getting 170mb/s at one point which Im happy with for a 5400rpm drive.

Thanks trurl, I did the post clear using the preclear_disk.sh -V /dev/sdX switch. It took a little longer than I had expected 27.42 hrs but no errors so Im happy about that.