disk bigger than the parity disk

[Fastcore]

Hi,

 

I would like to ask how to add bigger disk? My point is to add 8TB to array when parity is 4TB.

 

Of course it is understandable that it will use the half of capacity, but I think it shall be possible. 

 

Anybody knows how to do it ?

 

FC

[itimpi]

5 minutes ago, Fastcore said:

Hi,

 

I would like to ask how to add bigger disk? My point is to add 8TB to array when parity is 4TB.

 

Of course it is understandable that it will use the half of capacity, but I think it shall be possible. 

 

Anybody knows how to do it ?

 

FC

You have to upgrade the parity disk before you can add larger data disks as no data disk can be larger than the smallest parity disk.

 

If you have a failed data drive you can use the Parity Swap process to simultaneously upgrade the parity drive to 8TB and then reuse the old 4TB parity drive to replace the failed data drive.

[Fastcore]

Sure, but it is not my point. The idea of unraid is to use every disk which can be smaller or equal the parity. Why not bigger

 

It is very good question regarding emergency or just flexibility of this product. 

 

Additionally if someone would like to use ssd as the parity for eg. 4TB, equal 4TB HDD can not be added because it's slightly bigger. 

 

For me it makes nonsense.  

[Michael_P]

Why can't I put 10lbs of crap in a 5lb bag? Not enough room.

[Fastcore]

I see you don't understand the problem 

[apandey]

1 hour ago, Fastcore said:

Anybody knows how to do it ?

It cannot be done with the way how unraid is coded today. It's not a support issue, you are asking for a feature request from unraid developers

 

As far as I see, coding it is effort for a very niche use case. Anyone having a bigger disk can do a parity swap and end up with same amount of storage that you are proposing. With additional benefit that every subsequent disk addition can benefit from larger parity

Smaller faster disk has some merit, but again, write speeds are limited to combination of parity+data disks, so marginal utility

 

If you can convince enough people, it might get added. If not, you need biggest disk as parity today because of how parity works and unraids decision to allow people to be able to use all of their data disks (assuming there are always equal or more data disks than parity disks in most cases anyway) 

[Fastcore]

Understood, thank you.

 

I believe this shall be good feature. All bigger disks could be format to parity disk size.

 

Best regards 

[Kilrah]

12 minutes ago, Fastcore said:

All bigger disks could be format to parity disk size.

But then you'd be wasting useful space that you could use by just doing a swap. No point. 

If you have a single bigger drive it would be the same, any more and you're losing more space.

Edited February 6, 2023 by Kilrah

[Fastcore]

Sure. Of course it is lost, but I think it could be very useful for certain situations.

[itimpi]

19 minutes ago, Fastcore said:

Sure. Of course it is lost, but I think it could be very useful for certain situations.

You need to give a good Use Case where the Parity Swap procedure would not be sufficient.

[Kilrah]

20 minutes ago, Fastcore said:

for certain situations.

Which?

Nobody is going to spend significant development time because "it makes no sense but maybe someone somewhere might want it anyway".

[Fastcore]

enclosed example - this seagate is 0.02 GB bigger - can not be use.

[Fastcore]

On 2/6/2023 at 1:44 PM, itimpi said:

You need to give a good Use Case where the Parity Swap procedure would not be sufficient.

Of course it is, but:

1. All unraid operations are time consuming - if you want add a bigger or replace defected with bigger (what is most common because people buy always bigger) then you need: swap parity what will take lets say 12-20 h (if we talk of 8T), then install old parity as array member what will take another 5- 10h (if we talk about 4T); of course time will be incensed if the array will stay working.

2. It's the rule in raid systems to use equal or bigger disk to replace or extend. In my opinion could be applied also in unraid.

[apandey]

On 2/17/2023 at 1:50 AM, Fastcore said:

enclosed example - this seagate is 0.02 GB bigger - can not be use.

This example is an interesting one, but not necessarily a good use case for what we are discussing. No one makes a 4.02TB drive, so the question here should be how to tackle the discrepancy in disk metadata and what is causing it in first place. Maybe LT just need to handle that 

15 hours ago, Fastcore said:

It's the rule in raid systems to use equal or bigger disk to replace or extend. In my opinion could be applied also in unraid.

The big rule in unraid is to not waste the space like raid systems do and let one use the maximum disk space available when mixing drives. So while unraid can try to do all the things, it's the opposite of unraid's core focus. To add, raid systems anyway waste the time to build in addition to wasting space when you do it

 

15 hours ago, Fastcore said:

swap parity what will take lets say 12-20 h (if we talk of 8T), then install old parity as array member what will take another 5- 10h (if we talk about 4T); of course time will be incensed if the array will stay working

Maybe you can save some time for first disk, but then locked out for any further additions unless you keep wasting disk space on every addition from that point on. Given disk additions are rare events, what is the issue with time it takes? It's not like one needs to do array expansions multiple times a week. We do it once, let it finish and have an optimal system. This is no worse than any raid system disk addition with a better outcome on space utilization going forward

[Fastcore]

Yes, I can agree with all you have told and it's really not against my inquiry's. My scenario just gives to admin decision what to do and what is best way for certain situation.