I have a new unraid system setup. I haven't assigned any of the drives yet.

 

Which approach should I take:

 

1) Assign the data drives, start the array, copy all data over, then assign parity drive.

 

or

 

2) Assign the parity drive and data drives, start the array, copy all data over.

 

I want to do this as quickly and efficiently as possible.

 

Thanks.

Approach 1 seems to be the quickest to get the data copied onto the array.

If you know for sure the data drives have no bad sectors, and have no need to re-use the disks you are copying from (they can serve as your "backup" until the files are on the server) it will be much faster to copy to the array before a parity drive is assigned to the array.   That is the quickest.  

 

Just be sure to assign the parity drive AND initially calculate parity AND perform a parity check before you re-use the disks you were copying from.   Until you calculate and verify parity, you are not protected from a disk failure.

(the initial parity calculation WRITES to the parity drive, but you have no way to know all was written properly until yo then do a parity "check" by pressing the "Check" button on the web-interface.  That then READS the parity data to compare it with data READ from all the other drives.)

 

If you must re-use any of your source disks in the server, assign the parity drive and calculate/verify parity before you do so.  That way, you will have parity protection from a drive failure from that point onward.

 

Joe L.

Just be sure to assign the parity drive AND initially calculate parity AND perform a parity check before you re-use the disks you were copying from.   Until you calculate and verify parity, you are not protected from a disk failure.

(the initial parity calculation WRITES to the parity drive, but you have no way to know all was written properly until yo then do a parity "check" by pressing the "Check" button on the web-interface.  That then READS the parity data to compare it with data READ from all the other drives.)

 

If you must re-use any of your source disks in the server, assign the parity drive and calculate/verify parity before you do so.  That way, you will have parity protection from a drive failure from that point onward.

 

Joe L.

 

Thanks BRiT and Joe L. for your feedback.

 

Joe L., what's the consequence of not doing a parity "check" at that point? What is that something that could go wrong, and what is the consequence of that something?

 

Finally, if my parity drive is up and running and I later need to copy over large amounts of data, should I just "un-assign" the parity drive, copy the data, then reassign the parity drive?

Just be sure to assign the parity drive AND initially calculate parity AND perform a parity check before you re-use the disks you were copying from.   Until you calculate and verify parity, you are not protected from a disk failure.

(the initial parity calculation WRITES to the parity drive, but you have no way to know all was written properly until yo then do a parity "check" by pressing the "Check" button on the web-interface.  That then READS the parity data to compare it with data READ from all the other drives.)

 

If you must re-use any of your source disks in the server, assign the parity drive and calculate/verify parity before you do so.  That way, you will have parity protection from a drive failure from that point onward.

 

Joe L.

 

Thanks BRiT and Joe L. for your feedback.

 

Joe L., what's the consequence of not doing a parity "check" at that point? What is that something that could go wrong, and what is the consequence of that something?

If you do not do a parity check you will not know if parity was written to the parity drive in a way that could be read back correctly.  In other words, you have no idea if you are really protected by the parity drive.  We've seen cases where a parity check could not be made without errors.  If you can't perform a parity check without errors, you cannot re-construct a failed drive without errors.

Finally, if my parity drive is up and running and I later need to copy over large amounts of data, should I just "un-assign" the parity drive, copy the data, then reassign the parity drive?

No, I'd never un-assign the parity drive.  Not unless you are willing to risk a failure in one of your drives and not be able to reconstruct the failed drive.  I'm not willing to take that risk.

 

The write speed of the array today with modern 7200 RPM disks and good hardware is somewhere near 40MB/s.  This is way better than when unRAID first was released (about 4 1/2 years ago) and the write speed to it was between 8 an 10 MB/s.

 

Joe L.