Parity Drive Was Failing So I Replaced It With A Same Size SSD, Unraid Complains It Is Not The Biggest Drive

[crzynik]

Hi everyone, so I built this Unraid NAS a year ago with two 8TB HDDs (one as parity, one as a drive). For the last couple months the parity drive has been throwing a lot of errors and dropping offline so I decided to upgrade it to an 8TB Samsung SSD.

 

To do this I unassigned the parity drive, shut down, and then replaced it. Powered back up and tried assigning the Samsung drive to the parity slot and it is complaining that it is not the biggest drive. I am at a loss of what to do. I understand that it may be formatted differently and appearing as smaller, I couldn't find an option in Unraid to format it. 

 

These are the drive sizes: 

`Samsung_SSD_870_QVO_8TB_S5VUNJ0RA03845J (sdd): 7,814,026,532 KB (K=1024)`
`ST8000DM004-2CX188_ZCT2P6QP (sdb): 7,814,026,532 KB (K=1024)`

 

Any help is appreciated, thanks!

Edited January 6, 2022 by crzynik

[Squid]

There's physically more sectors on the HDD than there is on the SSD (ie: unless there's a HPA partition or something on the SSD, it is smaller than the hard drive and not much you can do about it.

 

You could always however post your diagnostics

[crzynik]

2 minutes ago, Squid said:

There's physically more sectors on the HDD than there is on the SSD (ie: unless there's a HPA partition or something on the SSD, it is smaller than the hard drive and not much you can do about it.

 

You could always however post your diagnostics

Thanks, they are the same size bytes wize. The SSD says it has an unkown partition format. 

[trurl]

7 minutes ago, Squid said:

post your diagnostics

 

[crzynik]

here are the diagnostics:

storagewhacker-diagnostics-20220106-1331.zip

Edited January 6, 2022 by crzynik

[crzynik]

Updated with the full zip folder.

Edited January 6, 2022 by crzynik

[Squid]

Follow the diagnostics link

[Squid]

Certainly appears to be the same size.  But it's probably a couple of sectors smaller than the original parity.  In that case you have to do a New Config to handle that situation.

[crzynik]

2 minutes ago, Squid said:

Certainly appears to be the same size.  But it's probably a couple of sectors smaller than the original parity.  In that case you have to do a New Config to handle that situation.

Thank you for taking a look, I appreciate it. A couple things:
1. I was advised that using an SSD as a parity drive is a bad idea. If this is the case, I may prefer to copy the HDD -> SSD and make the HDD my parity drive. 
2. If 1 isn't the way to go, would a new config entail data loss for the existing HDD? 

 

Thanks again for your help.

[Squid]

1 minute ago, crzynik said:

1. I was advised that using an SSD as a parity drive is a bad idea. If this is the case, I may prefer to copy the HDD -> SSD and make the HDD my parity drive. 

SSD's in the array:

 

- TRIM isn't supported on array devices, so write speed will always begin to suffer

- Since the parity drive is the only SSD, write speed will always be limited by the data drives same as now.

- Background garbage collection - Can't remember OTOH, but I think that if the drive doesn't support Deterministic Trim then the possibility of parity inconsistency will result caused by the drive itself.  @JorgeB can answer this better.  I believe that this isn't a "real" issue with modern quality SSDs

 

New Config's do not lose data.  It just sets the array in a state where it will rebuild Parity based upon the current data drive selections.

[trurl]

16 minutes ago, crzynik said:

copy the HDD -> SSD and make the HDD my parity drive. 

8 minutes ago, Squid said:

Since the parity drive is the only SSD, write speed will always be limited by the data drives same as now.

And if parity is HDD and the SSD is used as data, write speed will always be limited by the parity drive.

[crzynik]

12 minutes ago, Squid said:

SSD's in the array:

 

- TRIM isn't supported on array devices, so write speed will always begin to suffer

- Since the parity drive is the only SSD, write speed will always be limited by the data drives same as now.

- Background garbage collection - Can't remember OTOH, but I think that if the drive doesn't support Deterministic Trim then the possibility of parity inconsistency will result caused by the drive itself.  @JorgeB can answer this better.  I believe that this isn't a "real" issue with modern quality SSDs

 

New Config's do not lose data.  It just sets the array in a state where it will rebuild Parity based upon the current data drive selections.

I see, that is very informative. The issue being raised was with not being able to TRIM.

2 minutes ago, trurl said:

And if parity is HDD and the SSD is used as data, write speed will always be limited by the parity drive.

I would like to use the SSD as best I can. @trurl does that mean whether I use the SSD in the array or as the parity, it is a moot point (speed wise)?

In any case, I am thinking it may be better try to swap them and use the HDD as a parity drive, but I want to be sure I am making an informed decision. (If I were to rebuild this system, definitely would have done it differently storage wise lol)

[trurl]

I wouldn't waste an SSD in an array with HDDs myself. You can make a fast pool with it for caching or just as fast storage. That one is quite a bit larger than many would use for that purpose though, and no redundancy in a pool unless you add another of the same size.

 

If you want it in the array, I think it makes more sense to use it as a data disk. At least that way you will have SSD read speed.

[crzynik]

2 minutes ago, trurl said:

I wouldn't waste an SSD in an array with HDDs myself. You can make a fast pool with it for caching or just as fast storage. That one is quite a bit larger than many would use for that purpose though, and no redundancy in a pool unless you add another of the same size.

 

If you want it in the array, I think it makes more sense to use it as a data disk. At least that way you will have SSD read speed.

I already have two 256GB SSDs (pooled) that I use for my docker containers and what not, so these big drives are just for using as a time machine backup for my mac and also as other bigger backups, so it needs to go in the array somewhere. I think I'd like to put it as a data disk, is there a relatively easy way to move everything over to it from the HDD?

[trurl]

4 minutes ago, crzynik said:

is there a relatively easy way to move everything over to it from the HDD?

Assuming you don't want to involve any additional 8TB disks, I don't see how you can do this while maintaining parity. You could mount the SSD as Unassigned and copy the data that way.

 

On the other hand, with parity and a single data disk, they are already mirrors of each other, so you could conceivably New Config, swap their assignments (HDD to parity, SSD to data), trust parity, then disable the SSD data disk and rebuild it from the HDD parity.

 

We can get into more details of how to do that, but first:

 

Do you have backups of everything important and irreplaceable?

 

[crzynik]

3 minutes ago, trurl said:

Assuming you don't want to involve any additional 8TB disks, I don't see how you can do this while maintaining parity. You could mount the SSD as Unassigned and copy the data that way.

 

On the other hand, with parity and a single data disk, they are already mirrors of each other, so you could conceivably New Config, swap their assignments (HDD to parity, SSD to data), trust parity, then disable the SSD data disk and rebuild it from the HDD parity.

 

We can get into more details of how to do that, but first:

 

Do you have backups of everything important and irreplaceable?

 

I have already taken the existing parity drive out, so I will have to rebuild the parity either way. I added the SSD as a data drive and plan is to move all data over to it then put the HDD into parity and let the parity build. And yes, I have my shares quite organized and the only one that has data I need (not a direct backup of a device) I already have a separate copy of.

[trurl]

Sounds like a plan. You will have to New Config to reassign the HDD as parity.

[crzynik]

8 minutes ago, trurl said:

Sounds like a plan. You will have to New Config to reassign the HDD as parity.

Makes sense. I will update here when done. Just wanted to say thanks a lot, was quite stressed but found a solution that works for me and I learned a lot along the way. 👍