ZFS or UFS?

[tucansam]

Hi gang,

I would like Drobo/Netgear/etc functionality with Freenas... I think I will need to go with UFS, but I'm still reading and trying to learn. Given the below scenario, can Freenas accomplish what I am after?

Start with three 1TB disks. Add a fourth to increase space to the existing storage pool (ie for the sake of simplicity, assuming 2TB is available with three disks, storage increases to 3TB with the fourth). Later on replace the 1TB disks one at a time with 2TB disks and have the storage pool increase in side accordingly. Then 3TB, then 4, etc.

Basically I want the volume to stay the same by adding disks and replacing existing disks with larger ones, ie, not have to create additional pools based on different or larger disks.

Can this work?

 

[ProtoSD]

If you want the simplicity without the redundancy, then UFS is your answer. You can start with the 3 disks as ZFS, but you can't just add a single 4th disk unless you create another volume with it and that volume would not be part of the original 3 disk volume. So NO, in your specific scenario it won't work.

Once you create a vdev of a certain size (3 disks), you cannot change the number of disks in that vdev. A pool can have multiple vdevs. If you read the docs/faqs and TONS of posts asking this question, the info is all here in the forums.

 

[tucansam]

Thanks... I don't want to start a flame war, but is there a (free) software that offers this specific functionality? I do want redundancy, but part of why I am considering building my own (and not going with a turn-key from a major brand) is that I can then afford to build two identical systems and have them mirrored.

 

[Joshua Parker Ruehlig]

freenas is free and you can get that functionality with UFS like protosd.
There's also a ton of linux distors that could do the same thing.

 

[peterh]

Hi gang,

I would like Drobo/Netgear/etc functionality with Freenas... I think I will need to go with UFS, but I'm still reading and trying to learn. Given the below scenario, can Freenas accomplish what I am after?

Start with three 1TB disks. Add a fourth to increase space to the existing storage pool (ie for the sake of simplicity, assuming 2TB is available with three disks, storage increases to 3TB with the fourth). Later on replace the 1TB disks one at a time with 2TB disks and have the storage pool increase in side accordingly. Then 3TB, then 4, etc.

Basically I want the volume to stay the same by adding disks and replacing existing disks with larger ones, ie, not have to create additional pools based on different or larger disks.

Can this work?

I's start with a hope that emulating netgear seems a very silly idea. Their support and products has burned me.

What you want a way to increase your "pool" by replacing the disks with larger ones. To confuse the issue
you are also discussing the ability to add a single disk ( to the original 3 ) in order to increase storage. This
last reqirement is ill-conceived and should not be done.

increasing a zfs pool by replacing disks ( one at a time) is standard procedure. Just do it.
You may also increase a zfs pool by adding disks ( note the pluralis, you should add as many disks
that you have initially, 3 in your case. The two ways and probably mutually exclusive, there is no point
in increasing the number of disjs if you are going to replace them anyhow.

To answer your question ( as i interpret it ) yes, it's perfectly doable:
start with 3 disks in raidz ( raid5) then when these are full you have a choice to either :
replace the disks, one at a time, allowing resilvering to happen.
or
add 3 more disks as another "vdev" to your existing pool. These latter disks does not have to
be the same size and no resilvering is needed, you can start using them right away.
( you have the option to replace your original 3 disks with larger ones, but then 3 X resilvering
will be needed)

i's say "awoid resilver" it's time consuming and has a small risk of data loss.