Preclear before replacing drive?

[peteknot]

Hi guys. So I had a drive fail (no surprise since it was a WD green drive) and I'm going to replace it. Now I know when I put new drives into the array, it is good practice to use preclear a few cycles on it. But when it comes to replacing the drive, does this still apply? I guess I'm not sure what the rebuilding process does. From http://lime-technology.com/wiki/index.php/FAQ#How_do_I_replace_a_hard_disk.3F I can see that it seems that the process is mostly like adding a new drive to the array and therefore should be precleared. Thoughts/advice? Thanks.

[Joe L.]

Hi guys. So I had a drive fail (no surprise since it was a WD green drive) and I'm going to replace it. Now I know when I put new drives into the array, it is good practice to use preclear a few cycles on it. But when it comes to replacing the drive, does this still apply? I guess I'm not sure what the rebuilding process does. From http://lime-technology.com/wiki/index.php/FAQ#How_do_I_replace_a_hard_disk.3F I can see that it seems that the process is mostly like adding a new drive to the array and therefore should be precleared. Thoughts/advice? Thanks.

It is a good practice since it weeds out the drives that might fail in their first hours of use AND it identifies any un-readable sectors BEFORE you put your data on them.

 

It does not shorten then time the array will be off-line, since the array is online when a disk is being re-constructed even if a disk is not pre-cleared when being used as a replacement for an existing drive and a drive re-construction is occurring.

 

If you feel lucky, you can skip it, but roughly 1 in 5 drives seems to be defective from the factory...

Care to play the odds?

 

Joe L.

[garycase]

... no surprise since it was a WD green drive

 

Actually I've found that the WD Greens are very reliable IF you get past the "infant mortality" phase.  A ridiculously high % of these drives (~20%) will fail in the first few days if you stress test them ... but those that don't have problems there seem to be very reliable.  I always run the WD Data Lifeguard short test; extended test; write zeroes to the full drive; then repeat the short & extended tests; then run Spinrite at Level 2; and then run 2 cycles of Joe L's preclear script.    If there are ANY errors at any phase of that, or if it has ANY reallocated sectors, I RMA the drive for a new one 

 

As for your question, No, you don't need to pre-clear before replacing a drive ... pre-clear does NOTHING to aid in the rebuild process.    But you SHOULD thoroughly test the new drive you plan to use for the replacement ... and pre-clear may be one of the tools you use to do that testing.