Which drive to replace first?

[mightyball]

So my parity drive has been having some UDMA CRC errors (404 currently, doesnt seem to be rising lately). I replaced the SATA cable a while ago, but dont recall if it went up or not after that. I had a replacement drive i was going to put in, and move the old one to another NAS. But now one of my older data drives has 4 reallocated sectors on it. Which should I replace first? Is the parity drive with the UDMA errors ok to rebuild a new data drive? Parity was last checked this morning with 0 errors.

[phbigred]

Both are going to take time. Turn off anything that could be writing to the array. Pop out the parity and get that swapped. Order another drive to have on standby. Worst case you have a parity drive you can use for recovery should things go belly up. That's the route I would suggest. 

[Frank1940]

The UDMA CRC  errors are not a disk problem in 99.99% of the cases.   They are a transmission failure of the serial data failure between the disk drive and the SATA controller where the data is converted back into parallel data.  The data stream is sent with a check sum and if that check sum test fails the data is resent.  However, they do slow down disk operations because the correction process suspends further transfers until the error is cleared. 

 

I am assuming that the reallocated Sectors are very recent.  (These sectors themselves are not a problem because they will never have data stored on them again!)   If they are recent, they could be an indicator that the disk is entering a period of slow decline toward failure.    

Edited September 1, 2019 by Frank1940

[phbigred]

1 minute ago, Frank1940 said:

The UDMA CRC  errors are not a disk problem in 99.99% of the cases.   They are a transmission of the serial data failure between the disk drive and the SATA controller where the data is converted back into parallel data.  The data stream is sent with a check sum and if that check sum test fails the data is resent.  However, they do slow down disk operations because the correction process suspends further transfers until the error is cleared. 

 

I am assuming that the reallocated Sectors are very recent.  (These sectors themselves are not a problem because they will never have data stored on them again!)   If they are recent, they could be an indicator that the disk is entering a period of slow decline toward failure.    

Good point with the crc. I'd say Op go with your best judgement.