Raid with variable sized hdd's

[MichielG]

Hi,

I've been playing around with NASes for a couple of years now. First a synology one for 5years, then went to custom hardware with xpenlogy for 2 years but now thinking about switching to truenas because of lacking stability of xpenlogy and like to do some tinkering. Because synology has something what they call hybrid raid, I now have drives of different sizes. 2x 4tb, 2x 2tb, 1x 1tb. In my current setup I have 10 tb of usable space with data protection for 1 drive.

Is there a configuration (without buying extra) that would give me similar usable space and data protection?
Thanks in advance

 

[Arwen]

No.

A ZFS pool is made up of vDevs. Each vDev, (virtual device), contains the redundancy. With the disks you have, you can have a Mirrored pool like so;

2 x 4TB in a Mirrored vDev
2 x 2TB in a Mirrored vDev

That would only get you 6TB raw, with 4.8TB usable to keep pool at or below 80% used.

The single 1TB is not useful in this setup.


Every NAS / RAID scheme has it's strengths and weakness. Each owner / user has to choose which are both important and possible using what they have, (existing hardware or money).

 

[MichielG]

Thanks for the quick reply.
I accidentally made a mistake when summing up my hard drives. I have 2x 2tb, 2x 4tb and 1x 3tb. Is with that config something possible with some more usable space?
Also if I would configure these multiple vdevs, Is it then possible to make one big storage volume where I can put all my file in one spot?

 

[Spearfoot]

Thanks for the quick reply.
I accidentally made a mistake when summing up my hard drives. I have 2x 2tb, 2x 4tb and 1x 3tb. Is with that config something possible with some more usable space?
Also if I would configure these multiple vdevs, Is it then possible to make one big storage volume where I can put all my file in one spot?

The lady @Arwen 's answer still applies, regardless of the 5th drive's capacity. Any RAIDZ'n' vdev made up with your drives will be limited by the capacity of the smallest one.

With your five drives you can:

• Create two vdevs: 2x2TB mirror, 2x4TB mirror, for a total of 6TB usable capacity, not using the 3TB disk (as @Arwen explaned)
• Create a single 5-disk RAIDZ1 vdev, for a total of 8TB usable capacity (5 x 2TB less 1 parity disk)
• Create a single 5-disk RAIDZ2 vdev, for a total of 6TB usable capacity (5 x 2TB less 2 parity disks)

Whatever approach you take, you can always increase the pool capacity later, by replacing the smaller drives in the pool. Example: if you select RAIDZ2 and eventually replace the 2 x 2TB and 3TB disks with 4TB disks, your pool capacity will increase to 12TB.

Note that many users avoid RAIDZ1 pools made with modern 'large' drives, because of the danger of losing the pool during resilvering if a single disk were to fail and be replaced.

 

[Etorix]

Also if I would configure these multiple vdevs, Is it then possible to make one big storage volume where I can put all my file in one spot?

To clarify the next point, a pool can have any number of vdevs. So you can put then two 2*2 TB and 2*4 TB mirror vdevs into a single pool and the systems accessing your shares will see a single 6 TB storage space. As well as replacing the existing drives by larger ones, you can increase capacity by adding further vdevs—but ZFS will not rebalance the content across vdevs. With a further 3 TB drive (or larger), you could have 2*2+2*4+2*3 for about 9 TB of raw storage with protection against the loss of one drive.

 

[MichielG]

To clarify the next point, a pool can have any number of vdevs. So you can put then two 2*2 TB and 2*4 TB mirror vdevs into a single pool and the systems accessing your shares will see a single 6 TB storage space. As well as replacing the existing drives by larger ones, you can increase capacity by adding further vdevs—but ZFS will not rebalance the content across vdevs. With a further 3 TB drive (or larger), you could have 2*2+2*4+2*3 for about 9 TB of raw storage with protection against the loss of one drive.

Thanks for the explanation.
In the situation that you described, so 2x2+2x4+2x3, wouldn't there be protection against the lost of 3 drives (as long as it aren't drives in the same vdev) or doesn't it work that way when you put them together in a pool?

 

[Ericloewe]

It does work that way, but Murphy will ensure you lose both sides of a mirror.

 

[MichielG]

It does work that way, but Murphy will ensure you lose both sides of a mirror.

Haha thanks