[OpenIndiana-discuss] Switching from lzjb to lz4 compression

[Jim Klimov]

On 2013-06-26 22:01, Gary Gendel wrote:
> Hi,
>
> Can I switch from one algorithm to another on the fly?  I assume that
> only newly written data will be affected, but can the system deal with a
> mixed compression pool?

I believe it should be same as other compression algorithms
(though may be more complicated due to use of feature flags).
It was generally true that compression, checksums, copies and
such write-time attributes are basically applied per-block at
the time of write (i.e. if you zfs-send an uncompressed dataset
and zfs-receive it into a compressed target dataset, the newly
written blocks will be compressed).

It is not a problem to have different algorithms (including
"none"/"off" values) to be mixed in a single dataset, and of
course quite possible to mix them in a pool.

Another matter is the rpool dataset - it should use those algos
which are added into GRUB support so it can mount the root.
I believe LZ4 is among these (for source code versions of the
illumos-gate which offer LZ4 integration altogether).

HTH,
//Jim Klimov