... and adding 1 new drive that is 3 times larger than the drives removed.

 

So I have a number of 2 TB drives that are either under performing or running really hot relative to other drives.  Since now WD 6TB drives are on the market, it's now a possibility for me to actually lower the number of drives I have in my server (good for thermal/power/noise).  I am aware that I would have to make the parity drive the largest drive in the array.   

 

So my question to you unraid guru's is what is the order of operations I should perform to remove those drives/add 1 larger drive.  I know that during a parity rebuild, I will not have parity protection ...which is a risk I'm willing to take. 

 

Right now it takes my server about 24 hours to run a parity check (remember, under-performing drives are being replaced so this period should shorted substantially).

 

Any input is greatly appreciated.

 

Thanks,

Ogi

Preclear the 6TB drive/s, 53-63 hrs approx. There are various ways you can do it but I presume at the moment you don't have the space on the server to copy the data off the 3 x 2TB drives. If you do then its a lot easier to just do a new config. How big is your current parity drive? Give us some more information please ?

Sorry for the lack of info. Current parity drive is 3TB (so I'm going to need to preclear 2 6TB drives).  I do have enough free space on the server to empty out the 3 2TB drives (barely).

If you have at least two spare SATA ports (and enough power from the PSU), this is the way I'd do it:

 

* Preclear both new 6TB drives.

 

* Replace the old parity with one of the new 6TB drives. Add the other drive to the array (fast, once precleared).

 

* Copy the data from all 3 of the 2TB drives to the other 6TB drive. I'd use rsync and run a short test to see if mdcmd set md_write_method 1 is faster. On my setup, it's not.

 

* Run a parity check.

 

* Screenshot the current config and do a "new config".

 

* Remove the 3 2TB drives.

 

* Assign the remaining drives and build parity.

 

This way you will have a backup of your data (the data will still be on the 3x 2TB drives) during the parity build.

 

Before all that, I'd also back up any personal, irreplaceable or important data to an online service like OneDrive or Google Drive.

I'm in a similar situation.  I have one 1.5TB failed drive & have arriving a 3TB drive.  I also want to eliminate two other 1TB drives.  With the parity in tact, I copied all of the data that was on the failed 1.5TB, plus the two 1TBs to other drives (I have the room).

 

Can I simply pull the empty 1.5TB & two 1TBs, put in the new 3TB, restore and rebuild parity (unprotected)?  When one says "preclear" the drives, that is only if I care about protecting the array/parity during this process, right? 

When one says "preclear" the drives, that is only if I care about protecting the array/parity during this process, right?

Nope. preclear is a script used to prepare a drive to add into a new slot in an already parity protected array and avoid the lengthy downtime while unraid writes zeroes to the new drive to allow parity to be correct when the new drive is added. If you don't preclear the drive, the array is unavailable for the entire time (hours) instead of only being down to write the format to the new drive (minutes).

 

A highly desirable side effect of running preclear on the drive is that the script verifies that the new drive is good. A fairly high percentage of drives are either bad out of the box, or fail shortly after being put into service (google "bathtub curve" for more info). Many people using unraid will not put a drive into service without preclearing because of this confidence check. Unraid can only recover one bad drive at a time, so it's imperative that you have a high level of confidence in all the drives in your array.

 

I can't comment on the validity of your specific procedure without more information about all your current drive sizes. In any case, restore and rebuild parity doesn't make sense to me. Did you mean set a new configuration and rebuild parity?

Yes, I meant new config & rebuild parity.  Good point about the array being down if I start a parity from scratch.

 

Thanks for your help.

1 - Preclear both 6tb drives

2 - Simultaneously run a parity check

3 - Pull smart reports on all drives and verify all are healthy

4 - With array stopped, backup the config directory of you flash drive (I won't explain how in this post, but this backup can help you recover from an extremely unlikely drive failure when array is unprotected)

5 - Do a new config, reassign all your disks except parity (leave parity unassigned) and add one of the 6tb drives

6 - Start array. This array is unprotected. If you do no writes to any disk except the new 6t one you would still be able to recover from a failed disk with your backup config directory. Post back if you have a failed disk and need those instructions. You just ran a parity check and examined all your smart reports, the chances of a drive failure over the next day are hugely unlikely.

7 - Format the new 6tb drive in the array

8 - Copy your 3 2t drive contents to the 6tb drive. I'd recommend doing it on the server in a screen session (cp -Rpv ...)

9 - Verify data using md5sum or similar (optional)

10 - Stop array

11 - Do new config excluding unwanted 2t disks, using 2nd 6tb as parity. You can assign your old parity as a data drive if desired.

12 - Start array, parity will build. Do no writes to array.

13 - After parity builds, you can format your old parity (if you included it) and use the array normally. Delete your config directory backup. It is now dangerous to ever use it.

 

14. Parity check to confirm parity build.

I decided to go a bit off the reservation, since most of my unraid data is replaceable, and what is not, is backed up within the array and also outside the pc.

 

I copied all of the data (Midnight Commander) from the 3 drives I want to remove to other array drives.  Shutdown. Pulled the 3 drives, and inserted the new single 3TB drive.  Boot. New Config.  Currently running format of the new 3TB drive, & new parity check.

 

Obviously no protection for the (apparently) 6 days this will take, but I was willing to risk it.  Wish me luck.

this is what i'd do:

 

1. run parity check & preclear 6tb drives at the same time

2. mount one 6tb drive outside the array.

3. copy all data from the 3x 2tb drives to the 6tb drive.

4. perform new config with 6tb drive and 6tb parity drive.