[kwlug-disc] ZFS [was: Docker Host Appliance]

[Ronald Barnes]

Anyone with opinions or interests in ZFS could probably benefit from 
listening to the 2½ Admins podcast, specifically episode 123, where they 
do a ZFS Quick FAQ:

https://podtrac.com/pts/redirect.mp3/traffic.libsyn.com/latenightlinux/2.5admins-123.mp3

Starting at 22m55s.

"What are the questions people ask?"

"ZFS on a single disk?"
"Sure, it's okay - at least as good as any other file system."

"Non-ECC RAM okay?"
"No problem. Although preferred, regardless of ZFS."
"ZFS without ECC probably better than any other FS with ECC, since only 
ZFS can detect & heal errors."


"Do I need a ¿ slog ? or l2arc?"
"Probably not, unless..."


"How much RAM do I really need?"
"4GB is what I use.  More is better (when is it not?)."
"I used to run it with 1GB RAM; can still be done on a 1GB Linode VM."
"ZFS is not gonna be much busier in CPU than ext4."
"Avoid 32 bit though."
"I ran it on crappy (for the time) 2008 hardware."


"Can I use ZFS on a USB drive?"
"Yes.  But USB drives suck, especially for 24hour power up cycles."









Chris Irwin via kwlug-disc wrote on 18/01/2023 23.38:

> Now fast forward a few years of this VM doing it's thing, plus years 
> worth of rolling hourly/daily/weekly/monthly snapshots.
> 
> Does this not cause fragmentation on the storage? Your live file will be 
> nowhere near contiguous on the physical disk.
> 
> If "No": Please explain how ZFS avoids this. Because I haven't seen it 
> discussed.
> 
> If "Yes": This is the same fragmentation issue that people warn about 
> with BTRFS, causing them to say it can't do VMs, or you should disable 
> COW, etc.
> 
> I'm not saying fragmentation of storage is the end of the world. Read 
> ahead exists, caches exist. I'm just confused why BTRFS has a reputation 
> of doing VMs poorly when, as far as I can tell, ZFS has the same behaviour.


https://podtrac.com/pts/redirect.mp3/traffic.libsyn.com/latenightlinux/2.5admins-124.mp3 
at roughly 29m20s, Allan Jude and Jim Salter discuss storage solutions 
(@29m40s) Allan says, "ZFS-send to itself every 6 months for defrag" if 
you feel it's a problem.



> The only reason I can possibly think of that this wouldn't be an issue 
> on ZFS, is because it is so massively, massively RAM hungry

Not really. Not much more than other file systems, and that extra 
overhead means data corruption can be detected and repaired, so ... if 
your data matters, it's worth it.