Shrinking Array -> Adding Drives vs. Replacing Drives Procedure

[manofoz]

Hello,

 

I was thinking about shrinking my array via https://docs.unraid.net/legacy/FAQ/shrink-array/ so that I could then replace some 4TB drives with 20TB drives but this process seems tedious and I'm not sure it will be any faster than replacing a data drive one at a time https://docs.unraid.net/legacy/FAQ/replacing-a-data-drive/. The secound route will let me use the drives I want to replace until I'm ready to pop new ones in but won't let me replace all of the drives at once. 

Here are the drives I'm thinking about replacing, prbably 1-2 at a time, with 20TB drives:

 

They are all "empty" except for whatver the file system writes to them which is ~7% of their total space. Which is the least risky way to go here? Shrinking the array seems to add risk when you are clearing the drives and drive numbers getting reassigned etc. Replacing a drive seems to add risk by relying on Parity to rebuild a drive for you, though I do have 2x20TB parity drives. 

 

Probably shouldn't have added these 4TB drives in the first place as they do not provide much value but I am going to hit the high watermark point soon where they get written to and that would force me into the replacing-a-drive path. 

 

Thanks!

[manofoz]

I’m leaning toward replacing a data drive and doing them one at a time. I don’t need to upgrade them all at once, probably will do like two drives a month. 

[trurl]

Shrinking is for when you want to end up with fewer disks, usually with the data from the removed disk already copied to other disks in the array. It definitely is not faster.

 

And there is no way to replace your drives all at once unless you want to start again with empty drives.

 

Your first sentence says you want to replace, so upgrade is what you want to do. You could do 2 at once with dual parity, but simpler and safer to do one at a time as needed for capacity.

 

I always upsize my disks since I have no room for more disks, and I have done it many times. Replacing disks is the whole reason you have parity. Not risky at all if your array is working well. Just keep the original disk intact until you are happy with the rebuild.

 

In any case, you must always have another copy of anything important and irreplaceable. Parity is not a substitute for backups.

 

 

[manofoz]

2 hours ago, trurl said:

Shrinking is for when you want to end up with fewer disks, usually with the data from the removed disk already copied to other disks in the array. It definitely is not faster.

 

And there is no way to replace your drives all at once unless you want to start again with empty drives.

 

Your first sentence says you want to replace, so upgrade is what you want to do. You could do 2 at once with dual parity, but simpler and safer to do one at a time as needed for capacity.

 

I always upsize my disks since I have no room for more disks, and I have done it many times. Replacing disks is the whole reason you have parity. Not risky at all if your array is working well. Just keep the original disk intact until you are happy with the rebuild.

 

In any case, you must always have another copy of anything important and irreplaceable. Parity is not a substitute for backups.

 

 

 

Thanks! Upgrading it is. I've ordered 2x20TBs to start off with and will follow https://docs.unraid.net/legacy/FAQ/replacing-a-data-drive/. I got the 4TBs at a reduced price from a friend so I figured I'd give them a shot. They will hopefully be easy to upgrade over time so I can make this build last a while before I need to switch into something that can hold more drives. I just hope it doesn't take 24+ hours to rebuild the drive, or if it does that Plex at least stays functional.

 

After those I have other drives like 2x6TB I can replace so I should be able to squeeze a lot out of this. Technically my motherboard and case can support a few more drives but I'd have to get creative with how I mounted them (like replacing fans with drives...). 

[manofoz]

On 10/1/2023 at 9:11 PM, trurl said:

Shrinking is for when you want to end up with fewer disks, usually with the data from the removed disk already copied to other disks in the array. It definitely is not faster.

 

And there is no way to replace your drives all at once unless you want to start again with empty drives.

 

Your first sentence says you want to replace, so upgrade is what you want to do. You could do 2 at once with dual parity, but simpler and safer to do one at a time as needed for capacity.

 

I always upsize my disks since I have no room for more disks, and I have done it many times. Replacing disks is the whole reason you have parity. Not risky at all if your array is working well. Just keep the original disk intact until you are happy with the rebuild.

 

In any case, you must always have another copy of anything important and irreplaceable. Parity is not a substitute for backups.

 

 

 

Upsizing is in progress but man it's a lot slower than I expected. For one 20TB drive which replaced a 4TB drive with 1TB of data on it we are looking at 40+ hours! 

The drive is an Exos X20 specced at 280 MB/s, same as my parity drives. I first suspected my 5400 rpm drives were slowing the entire process down since everything was being read from at the same speed but those are only the other 4-6TB drives and it has since stopped reading from them, probably since it's past 6TB, and it didn't get any faster.

 

Just curious how this will work once we get 50TB hard drives. Will take a week to run partiy or replace a drive. 

[JonathanM]

On 10/6/2023 at 11:37 AM, manofoz said:

with 1TB of data on it

Amount of data is totally irrelevant, parity doesn't know anything about data, just the raw 1's and 0's that make up the entire drive.