What does "Copies" in ISO Installer mean?


Nov 3, 2017
Hi guys :)

One question came up when I installed on a test environment via Proxmox ISO installer...

I have 4 harddrives and went for ZFS RAID10. When I click on options, I get to choose the ashift, to activate compression and then there's a field with "copies" where there's 1 as default value.

What does this field do and is 1 the correct setting for a 4 drive ZFS RAID10?



Proxmox Staff Member
Staff member
Jan 7, 2016
see "man zfs":
       Controls the number of copies of data stored for this dataset.  These copies are in addition to any redundancy provided by the
       pool, for example, mirroring or RAID-Z.  The copies are stored on different disks, if possible.  The space used by multiple copies
       is charged to the associated file and dataset, changing the used property and counting against quotas and reservations.

       Changing this property only affects newly-written data.  Therefore, set this property at file system creation time by using the -o
       copies=N option.

       Remember that ZFS will not import a pool with a missing top-level vdev. Do NOT create, for example a two-disk striped pool and set
       copies=2 on some datasets thinking you have setup redundancy for them. When a disk fails you will not be able to import the pool
       and will have lost all of your data.

1 is the right value, unless you want to be extra paranoid and trade performance/space vs. redundancy


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