Question about hard disk replacement.

[Melocco]

I am in the middle of upgrading my drives (4tb sata to 6tb sas). But in the upgrade process one of the new drives stopped responding after the initial setup. So I tried to put my 4tb sata back in and it won't work. So now I'm down a drive (good thing I have two parity drives) and I can't put my old drive back in... 

 

If I upgrade and multiple drives start dieing (for example) I can't put the older 4tb drives back in. So am I stuck having to continue to use the 6tb drives? I don't have a big issue, but I'm running 20 drives. 

 

I guess just upgrade a few and keep the 4tb drives to replace bad 4tb drives. Buy a few 6tb sas or sata drives backups. Right?  

 

Just curious. What if I wanted to down size (ie. Go from 48tb to like 24tb. Smaller case etc.) would I need to just start over and build it smaller?

 

If there is no data on a drive (I use unbalance to move the data off that drive) & I'm not using the disk anymore, can you remove the drive from the pool without the errors? 

 

I know it's a crazy question, I don't have any issues yet but I'm thinking down the road. 

 

Thanks again for the advice. You all have been very helpful so far. 

[trurl]

Tools - New Config. It let's you assign any disks any way you want. Obviously you need to be careful to not put any data you want to keep in a parity slot. And of course, if you need to rebuild a disk this isn't the way to go since nothing is emulated after resetting the assignments.

[JonathanM]

Empty drives in the array are still part of parity protection, and can't be removed or downsized and still keep parity valid. An empty drive still contains lots of information, as the empty file system has the structures in place to organize and catalog data, all of which is part of parity. The only way to remove a drive without invalidating parity is force the write of all zeroes to the drive, which takes many many hours and results in an unmountable volume.

 

Because of this, it's generally a good idea to only keep drives that you actually need for storage in the array. Keeping a bunch of empty or little used drives in the parity protected array wastes resources and raises the risk of data loss unnecessarily. I generally try to keep enough free space in the array total as big as my biggest single drive. When I get below that, I upgrade my smallest disk. Try to keep the number of disks as low as possible, and always keep at least 1 physical and logical space permanently unoccupied in case of an emergency backup or recovery or testing option.

 

[trurl]

8 hours ago, jonathanm said:

An empty drive still contains lots of information, as the empty file system has the structures in place to organize and catalog data, all of which is part of parity.

And an empty disk (empty filesystem) still contains lots of bits that aren't even part of the filesystem. Every bit on a disk, to its full capacity, has a value, and all those bits are part of parity since parity just treats all disks as a bunch of bits.

[Melocco]

Ok.. So basically, if I wanted to down size, my only option would be: build a new system with smaller amount of drives.  Copy the data from one unraid to another. 

 

That's basically what I was asking. I think I understand. 

 

So basically, don't add larger drives until my drives are full. Have a few drives for each size incase of a failure.

 

Thanks for the advice. I guess I'm off to the net to buy a new mobo/kit (for new temp server) and minimum amount of drives needed. 

 

Again, you guys help me figure this stuff out.. 

 

 

[JonathanM]

21 minutes ago, Melocco said:

Ok.. So basically, if I wanted to down size, my only option would be: build a new system with smaller amount of drives.  Copy the data from one unraid to another. 

No, you have the option to remove drives, it's just that you will lose parity protection while you do that. It is correct that there is no way to rebuild to a smaller drive. Once a slot in the parity protected array is occupied, it can only be rebuilt from parity with identical or larger.  Removing slots (and the data on them) completely and rebuilding parity with the new layout is the only practical option to reduce array size. You will be unprotected from drive failure while you do that.

 

25 minutes ago, Melocco said:

I guess I'm off to the net to buy a new mobo/kit (for new temp server) and minimum amount of drives needed. 

If you wish to remain protected by parity and keep a full backup of your data during the transition, yes, that is the safest method.

 

That is why I stated to not include drives needlessly.

[Melocco]

Ok. So you said that I could, but would lose parity if I did... 

 

Is there a way to just remove drives, rebuild parity and be like i would need it? Or once the drive is in you have to replace it with that size or larger? 

 

I understand about replacing a smaller drive. Like a nas, you can't. But if I wanted to down size, how would I go about removing the drives with out the error staying there?

 

Is there terminal commands that I need to run? If so, where do I find that. Just trying to prepare incase I need to downsize. Right now I can't. I've got 36tb of data and 42tb of room (hence upgrading.) 

 

That's what brought me to ask these questions. Just in case. 

[JorgeB]

There are two ways to shrink an array, both described here:

https://wiki.unraid.net/Shrink_array

[trurl]

45 minutes ago, Melocco said:

Is there a way to just remove drives, rebuild parity and be like i would need it?

Already answered in the first response.

12 hours ago, trurl said:

Tools - New Config. It let's you assign any disks any way you want. Obviously you need to be careful to not put any data you want to keep in a parity slot. And of course, if you need to rebuild a disk this isn't the way to go since nothing is emulated after resetting the assignments.

When you change your disk assignments you should rebuild parity. That is the simpler and the first method explained at that wiki.

36 minutes ago, johnnie.black said:

There are two ways to shrink an array, both described here:

https://wiki.unraid.net/Shrink_array

[trurl]

Probably we should have just answered for your specific scenario, and that is actually what I was attempting to do in the first response I gave.

 

In your specific case, you would just New Config, assign the disks you want in the slots you want (including putting that smaller disk back in place of the larger disk). Then rebuild parity.

[trurl]

So, New Config is really the answer to all the possibilities you give in your first post.

 

Just be aware that New Config isn't going to do anything with your data. Nothing will be moved or rebuilt etc.

 

 It will just take whatever disks you assign and consider that your new array. Rebuilding parity after is optional but usually needed if you actually ever started the array with a different set of disk assignments.