[Discuss] Linux backups in 2019

[Rich Pieri]

On Sun, 10 Nov 2019 15:13:24 -0500
Daniel Barrett <dbarrett at blazemonger.com> wrote:

> On November 9, 2019, Rich Pieri wrote:
> >ZFS, snapshots, send/receive to make backups to external media.
> 
> ZFS looks *extremely* cool (haven't used it). Rich, any comments on
> its speed in real life for a desktop environment? ZFS appears much
> slower than ext4 on benchmarks like these:
> 
> https://www.phoronix.com/scan.php?page=article&item=ubuntu1910-ext4-zfs&num=2

Yeah. Their findings are kind of crap.

ZFS is a copy on write (COW) filesystem. Random access databases don't
play nice with COW filesystems if you don't tune both appropriately.
Phoronix did not tune anything appropriately.

ZFS wants lots of RAM for caches and most notably for the ZFS Intent
Log (ZIL). Without knowing the size of the zpool and the amount of RAM
in the system there is no way to tell if there is enough RAM or if they
need a separate cache device.

On my server at home? 4x4T WD Red drives in two mirrored vdevs plus a
64GB SATA SSD for cache. Sustained I/O is close to the mechanical limits
of the drives. Random and burst I/O are much faster due to the dedicated
cache device.

Aaron Toponce wrote pretty much the unofficial book on ZFS on Linux on
his blog. Definitely worth a bookmark if you do anything with ZFS.
https://pthree.org/2012/04/17/install-zfs-on-debian-gnulinux/

-- 
Rich Pieri