Mirror an exsisting Z2 8 drive array

[wheelsca]

I have a 8 x 4Tb array in Z2 and want to know if I can add another array the same and mirror the first without losing any data?

What steps would I take if possible.

Thanks,
Ron (Freenas newbie)

 

[Mihalich]

Do you want to add eight drives to make a mirror of RAIDZ2?

From manual:
When adding disks to increase the capacity of a volume, ZFS supports the addition of virtual devices, or vdevs, to an existing ZFS pool. A vdev can be a single disk, a stripe, a mirror, a RAIDZ1, RAIDZ2, or a RAIDZ3. After a vdev is created, more drives cannot be added to that vdev. However, a new vdev can be striped with another of the same type of existing vdev to increase the overall size of the volume. Extending a volume often involves striping similar vdevs. Here are some examples:

• to extend a ZFS stripe, add one or more disks. Since there is no redundancy, disks do not have to be added in the same quantity as the existing stripe.
• to extend a ZFS mirror, add the same number of drives. The resulting striped mirror is a RAID 10. For example, if ten new drives are available, a mirror of two drives could be created initially, then extended by creating another mirror of two drives, and repeating three more times until all ten drives have been added.
• to extend a three drive RAIDZ1, add three additional drives. The result is a RAIDZ+0, similar to RAID 50 on a hardware controller.
• to extend a RAIDZ2 requires a minimum of four additional drives. The result is a RAIDZ2+0, similar to RAID 60 on a hardware controller.

If an attempt is made to add a non-matching number of disks to the existing vdev, an error message appears, indicating the number of disks that are required. Select the correct number of disks to continue.

 

[wheelsca]

Thanks for the reply.

From reading I understand RAIDZ2 is pretty safe with a two drive failure possible, but lately in my world if something can go wrong, it will. I repair home computers for a living but am new to Freenas. I have had some customers ask if they can pay me to keep their data backed up when I reinstall their computers. I am looking for the best, fail safe way to do this. The last thing I need is to lose a customers data.

Am I really safe with the 8 x 4tb Z2 in an external case or should this be mirrored for extra safety? What are the odds of a complete Z2 failure?

Thanks again,
Ron

 

[Stux]

Set up another pool and replicate one to the other. Preferably on a separate machine.

Then you can tell your customers that their data is double backed up to multiple dual redundancy high integrity data pools.

 

[Mihalich]

We are talking about a complete failure of two disks in RAIDZ2, but the array will continue to work. For greater reliability, you can use RAIDZ3 or replicate data from freenas to another server.