0+1 Volume

[brianjg]

Hi,

I've got a mix of drives: 2 X 2TB, 2 X 1TB, I'm trying to create a 0+1 volume (I'm aware of the differences and issues with this vs 1+0 but I'm not in a position to add more disks). I can create a striped volume of 2TB+1TB but I'm stuck when trying to add the mirror.

Using the GUI seems to only give me the option of extending the volume with the remaining disks but it doesn't setup as 0+1.

Is this possible at all or can I do it via the CLI?

Thanks

 

[dlavigne]

I think you need http://doc.freenas.org/9.10/storage.html#manual-setup.

 

[Ericloewe]

Wait. Are you trying to mirror two vdevs? You can't do that, it's not possible. Vdevs are always striped.

Best you can do is one vdev with the 2TB drives and one with the 1TB drives.

 

[brianjg]

Well I was trying to create a stripe 2tb+1tb and have that mirrored by the other pair, however I achieved it was pretty much irrelevant, to maximise the storage usage and throughput.

I have an underlying hardware controller so I can in theory create 2 RAID1 arrays at the physical layer and then stripe them at the FreeNAS layer.

I read through the doc link provided but again didn't see how to do this entirely with FreeNAS.

 

[snaptec]

Don't do that. FreeNAS must have direct Access to disks.


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[brianjg]

hmm, I think I'll need to skip FreeNAS & use something else. Thanks anyway for everyones input.

 

[Arwen]

hmm, I think I'll need to skip freenas & use something else. Thanks anyway for everyones input.

Yes, FreeNAS is not as simple as other options. Many of us here like ZFS for the volume management, data integrity and some flexability, (ZFS is not the most
flexable option out there).

You can create a mirror vDev for each size of disk. Meaning the 2 x 1TB disks will be mirrored. Then the 2 x 2TB disks will be mirrored. This will give you the
3TB, (raw), space. ZFS will then stripe writes across the 2 vDevs, based on how much free space is available on the vDev. That means the 2TB mirror will get
more writes. But then, ZFS has to since the 2TB mirror has more storage.

Last, ZFS is the RAID solution. Using a hardware RAID device, (card or external chassis), is not recommended. That said, in big business world, it's done all the
time. We expose EMC type RAID LUNs to a server and use ZFS to stripe those LUNs. ZFS does not get us the ability to replace disks, it's handled in the EMC.
But, we do get all the other goodness of ZFS.