Hardlinks across a Multi Pool Devices

[wacko37]

I have my current downloads share on a single Pool Device formatted in xfs, which I'm currently thinking about future expansion which has lead me to a few questions.

 

1 - If I add a 2nd drive, from what I have read I will need to format to btrfs (as its the only supported format in multi device pools), which I would then covert to RAID 0 as I do not require any fault tolerance.... Is my logic correct?

 

2 - I'm aware that Hardlinks do not transfer across hdds/devices, But if i setup the above pool will hardlinks transfer across the hdds in the raid 0 pool?

 

 

 

Edited August 17, 2023 by wacko37

[JonathanM]

Each pool is a single entity with regards to file system, so hardlinks don't know or care about the individual disks in a pool.

 

RAID0 with 2 members will give you double the space of the smallest member. Single profile will add the 2 members together. Either will cause a total loss of data on the pool if either member fails.

 

New versions of Unraid allow ZFS as well as BTRFS for multi member pools. ZFS may be more reliable than BTRFS, I haven't had very good luck with BTRFS.

 

Any file system change to the pool requires backing up any content as the format will erase all data. Changes in BTRFS profiles may be able to be done without reformatting, but backups are still recommended.

[wacko37]

13 minutes ago, JonathanM said:

Each pool is a single entity with regards to file system, so hardlinks don't know or care about the individual disks in a pool.

 

RAID0 with 2 members will give you double the space of the smallest member. Single profile will add the 2 members together. Either will cause a total loss of data on the pool if either member fails.

 

New versions of Unraid allow ZFS as well as BTRFS for multi member pools. ZFS may be more reliable than BTRFS, I haven't had very good luck with BTRFS.

 

Any file system change to the pool requires backing up any content as the format will erase all data. Changes in BTRFS profiles may be able to be done without reformatting, but backups are still recommended.

Thanks so much for the reply and your time.

 

So if I understand you correctly,

 

Hardlinks - not a problem as the pool acts a single device/HDD. This makes sense just needed to be sure.

 

Regards zfs, heard and read so much about this filesystem. But leads me to more questions.....lol

 

My system is using non ECC ram - I remember reading that it's very important to have ECC ram with zfs - would it matter?

 

Also, I have a cache pool of 2 X nvmes that are in btrfs, I don't remember seeing an option for zfs, do cache pools allow zfs also?

[JonathanM]

3 minutes ago, wacko37 said:

My system is using non ECC ram - I remember reading that it's very important to have ECC ram with zfs - would it matter?

No more important than any other file system on Unraid. Unraid runs the entire OS from RAM. ECC theoretically freezes the system if it can't correct an error, limiting damage to files in use at that point. Regular RAM can keep running silently corrupting data in the background. Doesn't much matter which filesystem. If you are ok running Unraid with standard RAM, don't stress over ZFS.

 

8 minutes ago, wacko37 said:

I have a cache pool of 2 X nvmes that are in btrfs, I don't remember seeing an option for zfs, do cache pools allow zfs also?

6.12.X added ZFS, either for single member parity array disks, or pools, which can have multiple members.