Adding two 4tb drives to an existing pool

[Rio Rebel]

I am reading as much as I can and getting much of it down, but I can use a little reinforcement on what I want to do.

I have FreeNAS-9.3-STABLE-201412091831 running on a server with a G2120 Pentium (3.1ghz) and 8gb ram. My current configuration is three 2TB drives in raidz, and the performance is very solid. I am getting ~100mb/s read and write speed. Right now, I have two 4TB drives in a NAS box - Zyxel NSA320 - mirrored in a raid 1 configuration, and its performance is acceptable for a home NAS but nowhere near the FreeNAS server. I'd like to just pull these and add them to my server. I do not have the option of purchasing any new drives for a month or two.

Can I add a new vdev with the two 4tb drives in a mirrored array, thus adding ~4tb to my current zpool? I would have two vdevs - the current raidz with the three 2tb drives, and a second vdev with the two 4tb drives mirrored. Would this zpool then stripe across the two vdevs, giving me almost 8tb of available space?

Will this work? If not, what other suggestions do you have? Is it an option partitioning the two 4tb drives and making a 5 drive Raidz2, and if so, can the remaining partitions be used for anything?

Thanks!

 

[SweetAndLow]

I'll start by saying yes it will work to add a new vdev of the 2x4TB in a mirror.

other things i'll point out are, you should think about moving away from raidz1 it has issues with reliability during resilvering. Also if you created a 5 drive raidZ2 you would only be able to use 2TB out of the 4TB on each for the 4TB drives, creating a pool of ~6TB. You could then expand the 2TB drives to 4TB drives and once they are all 4TB you will have ~12TB total storage.

 

[Rio Rebel]

Thanks for the reply. I'm having second thoughts about adding the vdev. If I put the two 4tb into a 5disk radz2 with the others, could I partition them so that I would have 2+2+2+2(partition)+2(partition) and then use the two "extra" partitions to create a storage pool to use for another purpose?

 

[Ericloewe]

I have no idea what you're trying to do.

You cannot expand vdevs.

You must dedicate drives to vdevs.

You can "partition" a pool however you like, using datasets.

 

[danb35]

Thanks for the reply. I'm having second thoughts about adding the vdev. If I put the two 4tb into a 5disk radz2 with the others, could I partition them so that I would have 2+2+2+2(partition)+2(partition) and then use the two "extra" partitions to create a storage pool to use for another purpose?

Is this technically possible? Yes, it is, though you'd have to do it from the CLI. Is it a good idea? Not in the least, largely because the GUI's going to be awfully confused about what you just did. If you did 3 x 2 TB + 2 x 4 TB RAIDZ2, you'd have 6 TB of net capacity, and could later replace the 2 TB disks with 4 TB disks, resulting in 12 TB of net capacity.

 

[Rio Rebel]

I have no idea what you're trying to do.

You cannot expand vdevs.

You must dedicate drives to vdevs.

You can "partition" a pool however you like, using datasets.

I need to rethink what I'm doing, and suggestions would be very welcome. My goal is to take my existing drives - 3 2tb drives and 2 4tb drives - and create accessible, moderately reliable storage with high write speeds to transfer movie files (mkv and iso) in particular. I have just under 3tb of data right now, and my current configuration is the three 2tb drives in raidz on FreeNAS, and the two 4tb drives in Raid1 on the NAS box. The NAS box has been highly reliable and accessible from all devices on my network, but it is does not transfer as quickly as the FreeNAS box. For months, this FreeNAS box was being used as a linux fileserver (Mint 16), but I never got proficient enough at Linux and I had consistent problems with other computers recognizing the drives on a network and found raid on linux to be quite complicated.

Bottom line: I would like to continue to get my current level of performance on the FreeNAS box (~100mb/s writes) with more capacity than I have now. It seems to me that having the two 4tb drives in a mirrored NAS is a bit of a waste now, and I'm trying to decide how I can pull them out of the NAS box and use them in the FreeNAS server. I'm open to different possibilities, but do not want to purchase more drives at this point. That's the main goal.

danb35, thanks for your answer as well. Since I am not highly proficient with linux, I am going to take your advice and avoid complex scenarios that confuse the GUI (the way FreeNAS GUI does some of this for me is a big reason I am using it).

 

[Ericloewe]

A single RAIDZ2 vdev is probably your best option. Your next purchase would be extra 4TB HDDs, since the current ones will be limited to the size of the smallest drive in the vdev (2TB). This gives you roughly 6 drive manufacturer terabytes, as danb35 explained.

You can also do RAIZ1 + mirror, but reliability would suffer.

 

[Rio Rebel]

I think you've convinced me. Two other questions:

1. Since I would need to completely rebuild the raidz array, I would need to be able to store the data somewhere while building it. It is my understanding that I need to add all 5 disks to the array and cannot add later, so having a place for the data to sit while I build the raidz2 may be an issue. This would leave me with no backup, something I had not considered until now.

2. What about the possibility of a 4 disk raidz and using one of the 4tb drives as a backup? That would give me ~6tb of usable space on FreeNAS and still have a 4tb backup available.

 

[Ericloewe]

I think you've convinced me. Two other questions:

1. Since I would need to completely rebuild the raidz array, I would need to be able to store the data somewhere while building it. It is my understanding that I need to add all 5 disks to the array and cannot add later, so having a place for the data to sit while I build the raidz2 may be an issue. This would leave me with no backup, something I had not considered until now.

2. What about the possibility of a 4 disk raidz and using one of the 4tb drives as a backup? That would give me ~6tb of usable space on FreeNAS and still have a 4tb backup available.

I think I'd rather trust a single RAIDZ2 vdev than a RAIDZ1 vdev plus a single drive as backup

 

[Rio Rebel]

Okay, thanks a lot for the advice. I'll start planning the build and figure out how to store the data while I'm building it.