February 20, 201214 yr Given the troubles I've had, might it be wise to destroy my array and start over again? #1 - do I need to preclear the drives in the array? I have 5x 3TB #2 - can I create the parity drive AFTER creating the array and copying my data?
February 20, 201214 yr Given the troubles I've had, might it be wise to destroy my array and start over again? up to you #1 - do I need to preclear the drives in the array? I have 5x 3TB I would #2 - can I create the parity drive AFTER creating the array and copying my data? yes
February 20, 201214 yr I have 3TB drives. Will that take 24 hours per drive to preclear? closer to 36 most likely
February 20, 201214 yr Author The manual says "you can run preclear_disk.sh script on a new drive before you add it to the array and unRAID will recognize that the drive already has zeros written to every sector and will only take the array offline long enough to perform a format which only takes a minute or two." These are drives right out of the packaging. Shouldn't they be good to go? The first one is at 2% after 7 minutes...
February 21, 201214 yr The manual says "you can run preclear_disk.sh script on a new drive before you add it to the array and unRAID will recognize that the drive already has zeros written to every sector and will only take the array offline long enough to perform a format which only takes a minute or two." These are drives right out of the packaging. Shouldn't they be good to go? The first one is at 2% after 7 minutes... The preclear script has two main purposes. The first (and reason its name is what it is) is to ensure that the entire drive is filled with only zeros. There is no guarantee that a freshly unpackaged drive will actually be full of zeros, as it only takes zeroing the very first bit of a drive to make it appear empty to a computer. Unraid must KNOW that every bit of the drive is zeroed out, because it uses the sum of all the bits across all the drives to make the parity calculation. Writing zeroes to the entire drive takes a good while, even under ideal conditions. The second use we unraid users put it to is to stress test the drive before committing our valuable data to it. By writing and reading all addresses on the disk and confirming that they were actually properly written, it exercises the disk hard, hopefully to the point of early failure if it has weak spots from the factory, or is just plain bad. It simulates what actually happens during a failed disk rebuild event, where all sectors of every disk are read to calculate what the missing disk contained. After the preclear disk confirms all zeros, it adds a special bit of data to the beginning of the drive to tell unraid that it's safe to assume the drive is all zeros. If that bit of data isn't there, unraid assumes the disk is dirty, and will write all zeroes itself. The point of the preclear is to allow the unraid management to skip the really long step when you add the drive to an already protected array. If you don't care about possibly losing data if a drive fails, for example if this machine really is a backup of other data kept elsewhere that you can simply copy back over, then by all means skip the preclear, skip adding parity for now, just assign the drives to data slots and copy your files over. After all the files are in place, then you can assign the parity drive, and allow the parity to be calculated from the existing files. Just keep in mind that if a drive fails before parity is built, all the data you copied to that drive will be lost.
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