Re: Limitations of rsnapshot-style backups (Was: Re: lazy old guy asks question)
David Christensen wrote:
> On 9/1/25 14:57, Karl Vogel wrote:
> > > > On Mon 01 Sep 2025 at 16:15:39 (-0400), David Christensen wrote:
> > > a. Set the ZFS backup file system property "dedup". This will enable
> > > block-level de-duplication, which can de-duplicate data more than hard
> > > links alone.
> >
> > This option eats RAM like candy, so make sure you have plenty.
>
>
> From what I have seen on FreeBSD ZFS, under load ZFS can consume as much
> memory as it needs. For storage servers, this is exactly what I want -- I
> paid for that memory, I want ZFS to use it. But, I have little experience
> with ZFS on workstations; where many processes are competing for memory.
> AIUI there are tunables for ZFS, so you have options.
If you set dedup, you need lots of RAM, or performance plummets
on writes.
If you don't set dedup, you can generally set options like:
# Min 512MB / Max 8GB Limit on ZFS RAM usage (ARC)
options zfs zfs_arc_min=536870912
options zfs zfs_arc_max=8589934592
in your /etc/modprobe.d/zfs.conf
For a lot of small workloads, 512M - 1G works well.
-dsr-
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