VBox vm running ubuntu-22.04 host ubuntu-21.10

[Ralf Mardorf]

On Sat, 15 Jan 2022 19:46:00 +0000, Dave Howorth wrote:
>One thing I learnt about zfs was that it *really* needs fast cache. SSD
>or better. Dunno the details I'm afraid. I wasn't the sysadmin, just
>the poor joe that had to live with appalling performance until they
>fitted some.

Hi,

as already pointed out before, I'm not an expert on this. However, all
payable HDDs nowadays are device-managed shingled magnetic recording
disks, known to cause issues for this kind of usage, see
https://en.wikipedia.org/wiki/Shingled_magnetic_recording#Device-managed
. However, for this kind of usage SSDs are asking for trouble, too.
In a RAID the maximal speed depends on the slowest SSD. A few pointers
on how SSDs do work, see
https://en.wikipedia.org/wiki/Solid-state_drive#Wear_leveling ,
https://en.wikipedia.org/wiki/Write_amplification ,
https://en.wikipedia.org/wiki/Wear_leveling .
In a RAID TRIM doesn't work anymore.

For raid you want CMR HDDs, see
https://en.wikipedia.org/wiki/Perpendicular_recording .

"Both technologies (SMR and CMR) have their justification and their
respective fields of application. Above all, you can rely on SMR if you
want large hard disks with lower material costs and usually lower
electrical power consumption, which serve as pure data storage devices.

For permanent writing activities and the transfer of large amounts of
data at high transfer rates, i.e. when the speed of large data
transfers is important, CMR hard drives are the better choice." -
https://www.reichelt.com/magazin/en/smr-cmr-which-hard-drive-is-best-for-which-purpose/

For my desktop PC I'm using SSD only, no RAID and even no pool based
file system, I'm mostly using ext4. For backups I'm using external SMR
drives, no RAID, no pool based file systems, mostly ext4, too.

I'm using Virtualbox as well as QEMU/KVM. While the wish to learn using
ZFS pools and "Just a Bunch Of Disks" or RAID approaches by using a
virtual machine, I suspect that VM performance issues are added to the
already mentioned disk type performance issues.

Regards,
Ralf