Pool configuration help

[giri98]

Hello guys i have two 2 TB segate compute drive, one 4 tb segate compute drive and one spare ssd 240 gb segate which configuration can i make in truenas?

 

[Arwen]

Welcome to the forums!

Not much. TrueNAS and ZFS does not have many options for mixed disk sizes. This is basically your main / only choice;

240GB - boot disk
2 x 2TB in a Mirror pool
4TB in separate pool, as unprotected storage, (like a backup of your Mirrored pool or media backed up elsewhere)

A few people come to TrueNAS, (formerly FreeNAS, but TrueNAS Core & SCALE are free to use), with just an idea for a NAS. TrueNAS and underlying ZFS do not support well, thrown together hardware. ZFS is designed for high reliability, but just using left over hardware may reduce reliability noticeably. Some consumer disk drives are actually in-compatible with ZFS because of various reasons, (TLER, SMR, spin down, etc...).

Many of us in the forums want reliability, recover-ability and data verification that ZFS gives us. So we tend to design our hardware to accomplish those goals, make our hardware choices conservative. And having to select hardware specifically for the task of a ZFS based NAS.

 

[Davvo]

@Arwen I was under the impression that you can use a bigger-sized HDD in a pool with smaller disks, you just lose the extra space.

If my belief is true he could go for a Z1 pool, understanding the inherent risks of single redundancy.
With 2 TB drives the chance of a failure during a (relativery short compared to bigger sizes) resilver are (relativery) lower.

Or, to achieve higher safety, he could do a 3-way mirror.

He could even use it as an hotspare, though I don't see more benefit than the previous options.

It could be a good compromise for his budget, and he would be able to put more money in a solid motherboard.

 

[giri98]

Or, to achieve higher safety, he could do a 3-way mirror.

Thanks for your reply what do you mean with 3-way mirror?

What if i consider to buy an extra 4 TB drive?

 

[giri98]

Welcome to the forums!

Not much. TrueNAS and ZFS does not have many options for mixed disk sizes. This is basically your main / only choice;

240GB - boot disk
2 x 2TB in a Mirror pool
4TB in separate pool, as unprotected storage, (like a backup of your Mirrored pool or media backed up elsewhere)

A few people come to TrueNAS, (formerly FreeNAS, but TrueNAS Core & SCALE are free to use), with just an idea for a NAS. TrueNAS and underlying ZFS do not support well, thrown together hardware. ZFS is designed for high reliability, but just using left over hardware may reduce reliability noticeably. Some consumer disk drives are actually in-compatible with ZFS because of various reasons, (TLER, SMR, spin down, etc...).

Many of us in the forums want reliability, recover-ability and data verification that ZFS gives us. So we tend to design our hardware to accomplish those goals, make our hardware choices conservative. And having to select hardware specifically for the task of a ZFS based NAS.

Thanks. Can i use the ssd for log cache instead and load the os on a 160Gb drive that a have ?

 

[Davvo]

Thanks for your reply what do you mean with 3-way mirror?

What if i consider to buy an extra 4 TB drive?

A three-way mirror it's a mirror composed by three drives.
For more info: https://www.ixsystems.com/wp-conten...age_Pool_Layout_White_Paper_February_2022.pdf

If you buy another 4TB drive you could either go with a pair of mirrors (mirror A composed by the 2TB ones, mirror B by the 4TB ones) or, if my belief that you can use different-sized disks in a vdev stands true, a Z1 or Z2 with 4 disks.

I suggest you the following reading:

Introduction to ZFS

This is a short introduction to ZFS. It is really only intended to convey the bare minimum knowledge needed to start diving into ZFS and is in no way meant to cut Michael W. Lucas' and Allan Jude's book income. It is a bit of a spiritual...

www.truenas.com

Can i use the ssd for log cache instead and load the os on a 160Gb drive that a have ?

You can, but you shouldn't and probably you don't need a SLOG either. For a SLOG you want to have a very specific kind of drives that have power loss protection.

Suggested reading:

Some insights into SLOG/ZIL with ZFS on FreeNAS

What is the ZIL? POSIX provides a facility for the system or an application to make sure that data requested to be written is actually committed to stable storage: a synchronous write request. Upon completion of a sync write request, the underlying filesystem is supposed to guarantee that a...

www.truenas.com

 

[giri98]

A three-way mirror it's a mirror composed by three drives.
For more info: https://www.ixsystems.com/wp-conten...age_Pool_Layout_White_Paper_February_2022.pdf

If you buy another 4TB drive you could either go with a pair of mirrors (mirror A composed by the 2TB ones, mirror B by the 4TB ones) or, if my belief that you can use different-sized disks in a vdev stands true, a Z1 or Z2 with 4 disks.

I suggest you the following reading:

Introduction to ZFS

This is a short introduction to ZFS. It is really only intended to convey the bare minimum knowledge needed to start diving into ZFS and is in no way meant to cut Michael W. Lucas' and Allan Jude's book income. It is a bit of a spiritual...

www.truenas.com

You can, but you shouldn't and probably you don't need a SLOG either. For a SLOG you want to have a very specific kind of drives that have power loss protection.

Suggested reading:

Some insights into SLOG/ZIL with ZFS on FreeNAS

What is the ZIL? POSIX provides a facility for the system or an application to make sure that data requested to be written is actually committed to stable storage: a synchronous write request. Upon completion of a sync write request, the underlying filesystem is supposed to guarantee that a...

www.truenas.com

Thank for your reply i think i will go for 160gb boot drive and i will buy new drive to do the two mirror vdevs. Can i add the 4tb mirror vdev to the pool later when i finally buy the new disk?

 

[NugentS]

Yes

 

[Arwen]

As others have said:

• Yes, you can use your 160GB drive for the boot drive
• Yes, you can have 2 Mirrored vDevs, one of 2 x 2TB and one of 2 x 4TB in the same pool, giving you 6TB raw storage
• Log devices, (aka SLOG), are not recommended unless you use NFS, iSCSI or synchronous writes.
• Cache drives, (aka L2ARC), are not suggested until you have maxed out your memory. Further, L2ARC cache drives have a very specific use, (making data that is accessed often available faster). So if your use case does not fall in to that case, you can actually slow your server down because L2ARC requires memory for it's directory.

 

[Etorix]

@Arwen I was under the impression that you can use a bigger-sized HDD in a pool with smaller disks, you just lose the extra space.

If my belief is true he could go for a Z1 pool, understanding the inherent risks of single redundancy.

Yes he could, and space would grow upon replacing both 2 TB drives with larger drives. But that would not be especially future-proof since raidz1 will only become less safe by going with increasingly larger disks.
It's better to get more drives and go for either a stripe of mirrors (flexible) or a raidz2 (or raidz3) of the desired width (more space efficient, but upfronts the costs of 4+ drives).