The Ubuntu kernel team recommends to have at least 4GB of free memory to
run ZFS on slow backing store devices for nominal performance. Since
there is OS overhead (kernel, userspace processes etc) a 4GB Raspberry
Pi will perform sub-optimally. Note that the document you referenced in
commet #1 states:
"Computers that have less than 2 GiB of memory run ZFS slowly. 4 GiB of
memory is recommended for normal performance in basic workloads. "
Once you start to add in ZFS options such as compression and/or run
scrubs on a slow device it is likely you may start to see high memory
pressure issues occurring. Hence we do not support ZFS unless you have
at least 4GB of memory free.
** Changed in: linux-raspi2 (Ubuntu)
Status: Confirmed => Won't Fix
** Changed in: linux-raspi2 (Ubuntu)
Importance: Undecided => Wishlist
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https://bugs.launchpad.net/bugs/1852119
Title:
Please add zfs modules to linux-raspi2
Status in linux-raspi2 package in Ubuntu:
Won't Fix
Bug description:
The 4gb RPI4 is more than capable of handling zfs.
( Even zfs root can be enabled manually with arm64 eoan builds using a
variant of the steps at
https://github.com/zfsonlinux/zfs/wiki/Ubuntu-18.04-Root-on-ZFS . )
Currently one has to install zfs-dkms for zfs support, but ideally one
would have zfs modules come with the standard arm64 kernel so that one
does not have to recompile zfs on the pi.
Example:
uname -a
Linux rpi4 5.3.0-1011-raspi2 #12-Ubuntu SMP Fri Nov 1 09:07:06 UTC 2019
aarch64 aarch64 aarch64 GNU/Linux
@rpi4:~$ zpool status
pool: bpool
state: ONLINE
status: Some supported features are not enabled on the pool. The pool can
still be used, but some features are unavailable.
action: Enable all features using 'zpool upgrade'. Once this is done,
the pool may no longer be accessible by software that does not support
the features. See zpool-features(5) for details.
scan: scrub repaired 0B in 0 days 00:00:00 with 0 errors on Mon Nov 11
13:50:14 2019
config:
NAME STATE
READ WRITE CKSUM
bpool ONLINE
0 0 0
usb-Samsung_Flash_Drive_FIT_0309318110004882-0:0-part3 ONLINE
0 0 0
errors: No known data errors
pool: rpool
state: ONLINE
scan: scrub repaired 0B in 0 days 00:01:21 with 0 errors on Mon Nov 11
13:51:39 2019
config:
NAME STATE READ WRITE CKSUM
rpool ONLINE 0 0 0
sda4 ONLINE 0 0 0
errors: No known data errors
dkms status
zfs, 0.8.1, 5.3.0-1011-raspi2, aarch64: installed
@rpi4:~$ cat /proc/cpuinfo
processor : 0
BogoMIPS : 108.00
Features : fp asimd evtstrm crc32 cpuid
CPU implementer : 0x41
CPU architecture: 8
CPU variant : 0x0
CPU part : 0xd08
CPU revision : 3
processor : 1
BogoMIPS : 108.00
Features : fp asimd evtstrm crc32 cpuid
CPU implementer : 0x41
CPU architecture: 8
CPU variant : 0x0
CPU part : 0xd08
CPU revision : 3
processor : 2
BogoMIPS : 108.00
Features : fp asimd evtstrm crc32 cpuid
CPU implementer : 0x41
CPU architecture: 8
CPU variant : 0x0
CPU part : 0xd08
CPU revision : 3
processor : 3
BogoMIPS : 108.00
Features : fp asimd evtstrm crc32 cpuid
CPU implementer : 0x41
CPU architecture: 8
CPU variant : 0x0
CPU part : 0xd08
CPU revision : 3
Hardware : BCM2835
Revision : c03111
Serial : ---
Model : Raspberry Pi 4 Model B Rev 1.1
@rpi4:~$ free -m
total used free shared buff/cache
available
Mem: 3791 883 2612 18 295
2836
Swap: 4095 0 4095
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