February 11, 20242 yr Hello, On my unraid server, i have this cache pool : It is 3x 1TB drives, with one mirror, for a total of 1.9 Tb useable capacity. On the unraid console, when i do : df -h I have this output : root@Yggdrasil:~# df -h Filesystem Size Used Avail Use% Mounted on rootfs 24G 1.6G 22G 7% / tmpfs 32M 2.2M 30M 7% /run /dev/sda1 58G 2.5G 55G 5% /boot overlay 24G 1.6G 22G 7% /lib overlay 24G 1.6G 22G 7% /usr devtmpfs 8.0M 0 8.0M 0% /dev tmpfs 24G 0 24G 0% /dev/shm tmpfs 128M 1.5M 127M 2% /var/log tmpfs 1.0M 0 1.0M 0% /mnt/disks tmpfs 1.0M 0 1.0M 0% /mnt/remotes tmpfs 1.0M 0 1.0M 0% /mnt/addons tmpfs 1.0M 0 1.0M 0% /mnt/rootshare (array disks here) cache 939G 23G 916G 3% /mnt/cache cache/system 933G 17G 916G 2% /mnt/cache/system cache/domains 1.4T 417G 916G 32% /mnt/cache/domains cache/appdata 916G 2.3M 916G 1% /mnt/cache/appdata cache/appdata/mosquitto 916G 256K 916G 1% /mnt/cache/appdata/mosquitto cache/appdata/grafana 916G 1.3M 916G 1% /mnt/cache/appdata/grafana cache/appdata/homeassistant 916G 93M 916G 1% /mnt/cache/appdata/homeassistant cache/appdata/mysql 916G 119M 916G 1% /mnt/cache/appdata/mysql cache/appdata/nginx 916G 1.0M 916G 1% /mnt/cache/appdata/nginx (etc for others containers) The "cache" is reported to be 939GB with only 23Gb used. I dont really understand this value. Is it because of ZFS ? I use Glances (with Homepage), and i can't show the correct size of the cache pool : It seems to be reported as the df command line. Really not a big deal, but maybe i can use this to learn something more. Thanks all, K.
February 11, 20242 yr Community Expert Because it's by dataset, look st the datasets and add them all, just domains dataset is using 417G, and note that those use GiB, GUI uses GB.
February 11, 20242 yr Author Hello JorgeB, Indeed, it is by dataset. But why the main one (cache) did not report the full size of the pool array ? It seems to only report one drive of the three. That is more that i did not understand. Maybe i could have done better configuring it ? Thanks, K.
February 11, 20242 yr Community Expert Solution Just now, Keichi said: But why the main one (cache) did not report the full size of the pool array ? Because as far as df can see there's no data there, data is inside the datasets, and datasets are separate zfs filesystems, for example if you try to move some data from one dataset to another a full copy will be done, instead of a move.
February 11, 20242 yr Author Ok, i understand. So it is impossible to report the full size of a ZFS cache pool, with the tool i use. Thanks for the help, and as always, you clear answer. K.
February 11, 20242 yr Community Expert 58 minutes ago, Keichi said: So it is impossible to report the full size of a ZFS cache pool, with the tool i use. BTW, if you need to get the used or free space from a zfs pool for a script or something, instead of df you can use: zfs get -Hp -o value available,used <pool name>
February 11, 20242 yr Author Thanks! But, this is for Homepage (https://github.com/gethomepage/homepage) which uses Glances integration (https://github.com/nicolargo/glances). I will ask directly on Glances' Github for more information. I just wanted to understand better the issue and from you gave me, something is possible : root@Yggdrasil:~# zfs get -Hp -o value available,used /mnt/cache 966035955456 963024068864 Values seem correct to me. Thanks again JorgeB! K.
October 6, 2025Oct 6 Have come across this as well, where a pool in raidz1 of 6 22tb drives is reporting in the web interface Main, a total size of around 80-90 TB (it varies), while zfs correctly reports 6x20T drives as 120T (with 20T used for redundancy, of course). As zfs becomes more integrated, definitely something I hope to see getting more accurate in the future.My other 2 zfs pools seem to be correct though, at least.
October 7, 2025Oct 7 Community Expert Please post the diagnostics and the output from zfs get -Hp -o value available,used <pool name>
October 8, 2025Oct 8 zfs get -Hp -o value available,used fast6049611791718427283594134544For comparison:zpool list fastNAME SIZE ALLOC FREE CKPOINT EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOTfast 120T 37.2T 82.8T - - 1% 31% 1.00x ONLINE -tower-diagnostics-20251008-1304.zip
October 8, 2025Oct 8 It’s interesting, it’s seemingly adding up the used/free numbers to make a total, so the “size” value keeps changing as the pool fills. 😂🤔
October 8, 2025Oct 8 Community Expert 1 hour ago, eadnams said:so the “size” value keeps changing as the pool fillsThat will happen if you have block cloned data (reflinks) and/or dedup is enabled.
October 8, 2025Oct 8 Interesting. That may explain it.Is there a way to remove reflinks? I did do a cp operation briefly a while back, which default to reflinks being used. The original files are long gone now.zpool get all fast | grep -i clon fast bcloneused 7.26G - fast bclonesaved 7.26G - fast bcloneratio 2.00x - fast feature@block_cloning active local Edited October 8, 2025Oct 8 by eadnams Added the reflink information
October 8, 2025Oct 8 Community Expert If the original files were gone, i.e., there's only one copy of each file, they should not show up as extra capacity, so likely there are still multiple copies of some files.
October 8, 2025Oct 8 Not that I can find. I was copying from a root folder outside a dataset, into a dataset. The root is empty now, just has the datasets in it.Mostly just like size reporting in the dashboard to be correct. Edited October 8, 2025Oct 8 by eadnams left out part of the explanation.
October 8, 2025Oct 8 Community Expert The dashboard should show exactly what that zfs command shows; the stats come from there.
October 8, 2025Oct 8 Right, makes sense. It technically is, I suppose.Any idea why it is inaccurate though?I found and removed the reflinked data, have never had dedup enabled, but it still isn't reporting the incorrect amount for "size", and the "size" reported on the dashboard keeps changing on writeszpool get all fast | grep -i clon fast bcloneused 0 - fast bclonesaved 0 - fast bcloneratio 1.00x - fast feature@block_cloning enabled local zfs get -Hp -o value available,used fast 61063925599472 26707992507152 NAME SIZE ALLOC FREE CKPOINT EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT fast 120T 36.5T 83.6T - - 1% 30% 1.00x ONLINE - raidz1-0 120T 36.5T 83.6T - - 1% 30.4% - ONLINE sdh1 20.0T - - - - - - - ONLINE sdn1 20.0T - - - - - - - ONLINE sdg1 20.0T - - - - - - - ONLINE sdk1 20.0T - - - - - - - ONLINE sdl1 20.0T - - - - - - - ONLINE sdi1 20.0T - - - - - - - ONLINE Edited October 8, 2025Oct 8 by eadnams
October 8, 2025Oct 8 Looking through this: https://github.com/openzfs/zfs/discussions/15232 It seems this is a known OpenZFS bug that occurs with expansion. The recommendation is to use "zpool" instead of "zfs" for correct sizes/used/available stats. "zfs" just... gives the wrong numbers.# zpool get free,allocated,size,capacity fast NAME PROPERTY VALUE SOURCE fast free 83.6T - fast allocated 36.5T - fast size 120T - fast capacity 30% -That is all correct.This is not:# zfs get -o value available,used fast VALUE 55.5T 24.3T root@Tower:~# Should I do up a bug report? Its not Unraids fault, but Unraid could use the accurate information instead, to mitigate the zfs bug. Edited October 9, 2025Oct 9 by eadnams Term clarification.
October 9, 2025Oct 9 Community Expert If the pool was raidz expanded the stats won't be correct; that's a known zfs bug, but the capacity should not change just by writing data, more info below:https://forums.unraid.net/topic/46802-faq-for-unraid-v6/page/4/#findComment-1537164
October 9, 2025Oct 9 25 minutes ago, JorgeB said:If the pool was raidz expanded the stats won't be correct; that's a known zfs bug, but the capacity should not change just by writing data, more info below:https://forums.unraid.net/topic/46802-faq-for-unraid-v6/page/4/#findComment-1537164Exactly. But it does seem to, as though its taking the "free" and "used" and just adding them together to get the total "size". But because the 'used' changes, and the 'free' doesn't always... Though we can grab the more accurate/correct info (see my second comment), to bypass the zfs bug regardless. Edited October 9, 2025Oct 9 by eadnams More details.
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