Expanding a Mirror

[JCasanova]

Hey all!

I'm new to Freenas and somewhat new to storage arrays.

ZFS seems pretty awesome. I like the scalability and granular configuration that it brings to the table.

I currently have a FreeNAS box set up with 2x 2TB disks and a 500 GB disk that is set as striped.

I am copying data that is on a 4 TB disk in another machine to this array (It'll just barely fit.)

Once the data is off of the 4 TB and verified to be a good copy, I will be looking to put that 4 TB into the FreeNAS box and attempt to expand that array. I also have a 250 GB drive that I was considering putting into the box as a cache or perhaps stripe...

What is the best method to do that? Will it expand the volume like I am expecting it to?

What would be the better use of that 250 GB disk?

The purpose of this NAS is multiple. While it isn't a production machine (It's my home personal education lab file storage) speed is not necessarily a requirement however I am running a VMWare ESXi host that is attached to this box via NFS for VM storage. So it'll need enough performance to run a few (2-3) VMs without choking terribly.

The bulk of the storage is media and a software library of various sorts and a lot of it does not get accessed often. What would be the best compression for the 3 datasets? (Media, software and VM repository)

 

[danb35]

I hope you mean that your 500 GB disk is a separate pool, rather than being striped with your 2 TB mirror. If the latter is the case, you're screwed--failure of that 500 GB disk will result in the loss of all your data in the pool. You have two safe options to expand a mirrored pool: (1)replace each disk, one at a time, with a larger disk, or (2) add another mirrored pair of any size disks. In the former case, you'll be left with a two-disk mirror of the larger size disks; in the latter case, you'll have two mirrors striped together (similar to a RAID 10 arrangement).

I can't honestly think of a good use for the 250 GB disk. For any sort of cache (L2ARC or SLOG), you'd want an SSD for it to have any value (using spinning rust to cache more spinning rust just doesn't make sense), and unless you've already maxed out your RAM, a cache device isn't likely to be of much benefit anyway. Maybe you could stripe it with the 500 GB disk for a (relatively) fast scratch pool?

 

[JCasanova]

So I should start from scratch with the two 2 TB disks in RAID 0, then copy the data from the 4 TB to that array, then add the 4 TB in as a mirror of the array? Is there any use for the 500 and 250 GB disks in this array or should I just use them as a second array?

 

[gpsguy]

You can't create a striped vdev with 2x2Tb drives and then add the 4Tb drive as a mirror to it.

So I should start from scratch with the two 2 TB disks in RAID 0, then copy the data from the 4 TB to that array, then add the 4 TB in as a mirror of the array?

 

[JCasanova]

You can't create a striped vdev with 2x2Tb drives and then add the 4Tb drive as a mirror to it.

Then I'll replicate the pool of 2x 2 TB disks to the 4 TB disk for a level of crude redundancy. I can't really think of a good way to go about it without adding more disks. (Not in the budget right now.)

 

[danb35]

There isn't any use that I can see for your 500 GB and 250 GB disks in this array. What you're proposing (stripe the 2 x 2 TB disks as one pool, set the 4 TB disk as a second pool, replicate from the one to the other) will work, even if it is kind of crude. Another option would be to set up RAIDZ1 with your 2 x 2 TB disks and 1 x 4 TB disk; in the future, you can replace the other 2 TB disks with 4 TB disks to expand the array. RAIDZ1 isn't really recommended, but this would give you real-time redundancy.

If you haven't already, check out https://forums.freenas.org/index.ph...ning-vdev-zpool-zil-and-l2arc-for-noobs.7775/ for some of the basics of ZFS.

 

[JCasanova]

Thanks. I don't think I'd have the option for a RAIDZ1 because I have to play hot potato with my data. The two 2 TB drives are empty but the 4 TB drive has the data that I need to copy to the array... no way to do that without nuking all 3 drives at the same time.

UPDATE: I'll probably end up just replicating the 2x2 array to the 4 TB and once I save up enough clams I'll buy two more 4 TB drives and build a RAIDZ1.

 

[danzi]

you could online your data to crashplan. The free version allows for one computer, unlimited data, and then rebuild your pool ad you want. Will take some time, but it is free and hot potato is never good with live data anyways


Sent from my iPad using Tapatalk