Re: Setting up ZFS L2ARC on a zvol

From: David Christensen <dpchrist_at_holgerdanske.com>
Date: Sat, 05 Nov 2022 18:59:13 UTC 
On 11/5/22 11:39, Steve O'Hara-Smith wrote:
> On Sat, 5 Nov 2022 10:39:53 -0700
> David Christensen <dpchrist@holgerdanske.com> wrote:
> 
>> ZPOOLCONCEPTS(7) for both 12.3-R [1] and 13.1-R [2]:
>>
>> "Virtual devices cannot be nested, so a mirror or raidz virtual device
>> can only contain files	or disks.  Mirrors of mirrors (or other
>> combinations) are not allowed.
> 
> 	Of course you can cheat to some extent using iscsi - I've used an
> iscsi mounted zvol as a zfs mirror for an SSD in a laptop.


Interesting.


I wonder if that trick would solve the OP's desire to create a ZFS 
volume on the NVMe pool and use it as a cache for the HDD pool?
And, if so, how to measure the additional CPU cycle and memory costs?



David