Ok this is my first go with unRAID but have been doing a lot of reading over the last few weeks. Committed to my kit list last week and it's all here and assembled. One of the tricky parts was choosing the 2TB drives as they all seem to have issues of some sort. I have ended up with 3 x WD EARS drives plus I have 3 x Samsung F3's on coming, avoiding the F4's for now.

 

Started a preclear today on one EARS drive, no jumper. I am using v1.6 of the script and unRAID 4.7. I was a little confused over the correct settings for this preclear but I had read that I should by using -A and in other posts it mentioned using the  "MBR 4k-aligned" option in settings. So I set the MBR-4K and ran the preclear without the -A.

 

So first question, is the above correct or should I have used the -A switch as well as the MBR-4K setting?

 

Second question, should I leave the MBR-4K setting on when I install and preclear the F3 drives?

 

Not sure if these are dumb questions, apologies if they are

 

TIA, Andy

Joe has posted that his script will recognize the 4k-aligned setting so if that was set before you started then I believe you would be ok. Hopefully, someone else can post the command to check the MBR record starting point.

 

You can use the 4k-aligned setting for every drive. It's NOT an advanced format drive only setting and will work fine for every drive except a WD EARS drive with a jumper. The setting just moves the partition 1 sector so the partition will be aligned on an advanced format drive. There is no such thing as a non-advanced format drive being misaligned.

 

Peter

fdisk -l -u /dev/sdx

 

Where x is the letter of the drive you want to check.  If the drive is 4k-aligned you'll see something like this:

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1              64   976773167   488386552   83  Linux
Partition 1 does not end on cylinder boundary.

 

If the drive is not 4k-aligned you'll see something like this:

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1              63  2930277167  1465138552+  83  Linux
Partition 1 does not end on cylinder boundary.

 

Note the different start numbers.

 

One of the tricky parts was choosing the 2TB drives as they all seem to have issues of some sort.

Not all of them do. 

So far the brand new 2TB Hitachi 5940rpm drives seem decent, but it's too early to make an informed decision on them.

Thanks guys for you assistance

 

Reading through Joe's preclear thread again the following statement I believe answers my question;

If you are running unRAID 4.7 onward, in the absence of either a "-a" or "-A" option specified on the command line, preclear_disk.sh will use the alignment preference you specified in the unRAID settings screen as its default. (-a will force MBR-unaligned. -A will force MBR-4k-aligned )

 

So if I set the MBR-4K option in the settings page, I don't need to add -A to the preclear script? Just got myself worried last night that I hadn't done this correcly as it takes soooo long if I need to do it again.

 

Looking at the preclear screen I can see that it has started on sector 64 so that is 4K-aligned

 

 

You are correct,

 

If you don't put a switch it will run the default. I tend to put the switch there all the time, just peace of mind.

 

Josh

Of course the default support requires that you're running a recent version of the script. It is always in your best interest to obtain the latest version of preclear_disk.sh immediately before you're about to invoke it.

Of course the default support requires that you're running a recent version of the script. It is always in your best interest to obtain the latest version of preclear_disk.sh immediately before you're about to invoke it.

 

Did exactly that

Just got myself worried last night that I hadn't done this correcly as it takes soooo long if I need to do it again.

Even if you would have done it wrong correcting it is only a matter matter of seconds.

I had to realign myself and this line fixed it.

preclear_disk.sh -C 64 /dev/sda

Just got myself worried last night that I hadn't done this correcly as it takes soooo long if I need to do it again.

Even if you would have done it wrong correcting it is only a matter matter of seconds.

I had to realign myself and this line fixed it.

preclear_disk.sh -C 64 /dev/sda

 

Thanks for that, very useful

Just got myself worried last night that I hadn't done this correcly as it takes soooo long if I need to do it again.

Even if you would have done it wrong correcting it is only a matter matter of seconds.

I had to realign myself and this line fixed it.

preclear_disk.sh -C 64 /dev/sda

 

What is the advantage of aligning at sector 64?

To get maximum performance out of these (AF) drives

Now I'm tempted to run this command myself.