On 8/10/21 12:56 PM, Dan Ritter wrote:
David Christensen wrote:
On 8/10/21 8:04 AM, Leandro Noferini wrote:
https://wiki.debian.org/ZFS
But:
- ZFS wants lots of memory. The rule of thumb is 5 GB of memory for every 1
TB of storage.
This is a myth.
Oracle says [1]:
"... for good ZFS performance, use at least one GB or more of memory."
The FreeBSD "ZFS Tuning Guide" says [2]:
"To use ZFS, at least 1 GB of memory is recommended (for all
architectures) but more is helpful as ZFS needs *lots* of memory."
"There are some resources that suggest that one needs 2GB per TB of
storage with deduplication ... . In practice with FreeBSD, based on
empirical testing and additional reading, it's closer to 5GB per TB."
(I use deduplication, so I recalled the "5 GB per TB".)
STFW there are other recommendations.
Looking ahead, I agree that deduplication does not make sense for the
OP's use-case. So, 1 GB of memory is supposed to be enough. Benchmarks
would be informative, but STFW I am unable to find such.
- ECC memory is safer than non-ECC memory.
This is true, but there is nothing that makes ZFS more dangerous
than another filesystem using non-ECC memory.
I think the amount of danger depends upon how you do your risk
assessment math. I find used entry-level server hardware with ECC
memory to be desirable for additional reasons.
- "dedup" is heavyweight, slow on HDD's (due to seek latency), and not
recommended for general workloads.
Not stated strongly enough. Nobody should turn on dedup; people
who think they are experimenting should definitely not turn on
dedup; only people who have a completely sacrificial system and
a good knowledge of the data to be stored should consider dedup.
This article has some good information:
https://www.truenas.com/docs/references/zfsdeduplication/
I have been running deduplication for several years on my SOHO servers,
which have HDD's and SATA3 SSD caches. Normal read/ write operations
can fill the Gigabit network, but replication is very slow (5.8 MB/s for
a recent replication job).
David
[1] https://docs.oracle.com/cd/E18752_01/html/819-5461/gbgxg.html
[2] https://wiki.freebsd.org/ZFSTuningGuide
