For all of the drives I've used for version 4.7, I've run preclear without the -A option.  I've also done nothing to the drives other than unpack them and install them in the server.  All of the (parity and data) drives are newer Western Digital Green drives, two 1.5 TB and one 1 TB (and will add another 1.5 TB green drive soon) for data and one 2 TB for parity.

 

For version 4.7 of Unraid,

 

1) Should I be running preclear with the -A option?

2) Should I be doing anything else for my advanced format drives?

 

I searched for this information, but the search results are confusing. 

Your drives are under 2TB?

 

Raj, I have two of these drives I'm about to preclear. However, I'm curious if you used the -A option in your preclear, to force the partition to start on sector 64 instead of 63. On my 3TB Hitachis I found they still needed to start on 63, and were using 512B alignment.

NO disk, regardless of manufacturer, will ever use an MBR style partition.  They will ALL use a GPT partition.

 

When a GPT partition is used, a protective "partition" is defined in the MBR to appease older utilities that only read the MBR and have no concept of disks larger than 2.2TB.

 

Therefore, on any disk over 2.2TB the preclear script will completely ignore the "-a" or "-A" option, or any "default" setting in the unRAID configuration for disks.   

 

Your 3TB Hitachi drives MUST have a GPT partition in unRAID.  If used in unRAID, they will have the protective partition defined that allocates the entire drive that was possible under the MBR partitioning scheme. 

 

That partition will be defined as starting on sector 1.   

 

Give it a try, type

fdisk -lu /dev/sdX

and see what it tells you. 

 

It could still be using a GPT partition to access the entire disk, but the "protective" partition would not be defined as expected.  If it is not re-defined by unRAID when a parity disk is not present, it is a bug in unRAID.    If it says the partition starts on sector 63, or 64, something is wrong with how unRAID is handling the protective partition.

 

As far as the pre-clear goes, it reads and writes the entire drive regardless of how you invoke it, so you don't have to re-do anything, other than if you expect the drive to be recognized as a valid pre-cleared drive to be added to an existing parity protected array.

 

Aligning to (64) 512byte sector boundary is a good idea, regardless of drive capacity or sector size.

Just use -A and no jumper. Use the -A for all drives.

Your drives are under 2TB?

 

 

I have a 2TB parity drive, two 1.5TB data drives, one 1TB data drive, and a 128GB SSD cache drive.  All are in use, and for none of them did I use the -A option.  Will likely add another 1.5TB data drive, though I may keep this as a hot spare. 

 

If I should've used the -A option for preclear, how do I go about "undoing" this to make each drive correct?

 

Thank you.

Just use -A and no jumper. Use the -A for all drives.

 

If my drives are already in use, do I have to redo the preclear with -A? 

 

I have another drive coming, which I'm considering using as a hot spare.  So, theoretically, I could preclear this drive with -A, then move data from a data drive to this drive, preclear the data drive with -A, and continue this process for all of my data (and parity?) drives.  It would just take a while.  I just precleared my 2TB parity drive, and it took over a day to do that.  To redo preclear on my four drives (three data and one parity) would likely take four-five days.  I'm willing to do that if the speed of the array would improve. 

You can do that or you can just leave them if they're working fine for you. The gains really aren't much. If you do cycle through swapping them out then run the preclear with the switches to skip the pre-read and the post-read. It would then clear a 2T drive in about 8 hours.

Great, thank you.  I might as well do it, as I'm also thinking of upgrading to a higher version of the software.  And, once the new drive is installed, it should be that most of the time will be spent waiting (e.g., launch a preclear script and wait until it's done). 

 

I've had a few issues, one I can remember is where I was making a backup from the unraid server to one of my computers; on another computer, I tried to watch a TV show stored on the unraid server, and I could not do it.  However, this isn't an easy situation to debug and I don't know whether the speed of the unraid server was an issue.  But any increase in speed might be beneficial, as the unraid server handles all the music, DVD, Bluray, TV, files, etc., throughout the house.