I have a running freenas zfs on raid-z1. For safety i though of increasing parity. Enough spare space is available.
Is it possible to upgrade a zfs raid-z1 to raid-z2 or raid-z3?
thx for your help
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As explained by Shane, you have to determine the RAID-Z level on creation. the RAID level cannot be changed at any time later. It may be changed by recreating the raid, however. Adding drives to a RAID-Z is also limited and should be avoided.
NEVER, ever add a single drive to a RAID-Z.
Adding a single HDD to a RAID-Z is a really bad idea. Assuming the first RAID-Z is full and ZFS stripes data, all data is written to the single drive. The single drive does not have any mirror and thus may get lost on a failure. Thus, it does not provide any integrity or parity correction!
This is possible, but probably not recommended either. Adding drives to an existing RAID-Z will create an additional RAID-Z and stripe the data over both RAID-Zs. If the first RAID-Z is full, all data will be written to the newly-added RAID-Z. ZFS does not rebalance the data. If you'd like to get a performance increase by adding new drives, you are probably better off fully recreating the RAID.
A really good explanation why can be found in the blog post ZFS: You should use mirror vdevs, not RAIDZ.
Simplified, there are several reasons:
This is just for completeness. I'm not affiliated with Rockstor or FreeNAS, just evaluating both for myself.
ATTENTION: As of Aug. 2016, btrfs has bugs in the raid code and is not stable. As I understand it, consider only using it with stripped mirrors.