ZFS special device

[sub2o5]

Hello,

i found several pages on the net stating the specialdevice gets around 75% used per default, but this setting can be changed.
No one mentioned where this can be done, i only found one setting with 75 for l2arc, which, obviously, is something different.

Does anyone know more?

I also know, that you can't remove a specialdevice BUT you can add additional specialdevices, much like in regular RAID10 ZFS.

But can you also add a larger specialdevice (either to the vdev mirror or as separate vdev) AND then, after sync, remove the old specialdevice for additional space?

I would really appreciate some clarification as i've chosen some slightly to small ssds for the specialdevice and may run into the 75% limit soon.

Kind regards
Stephan

PS: This is a crosspost - i also posted to the national proxmox forum and tried to translate as good as possible. I'll share the answers in both threads, of course!

 

[sub2o5]

Quick follow up:

you can simply increase the size of your specialdevice by setting "autoexpand=on" and adding bigger mirrors. After removing the last small device, the specialdevice automatically gets expanded to the next bigger devs!

 

[timeltdme]

i've chosen some slightly to small ssds for the specialdevice and may run into the 75% limit soon.

bit of an old post, but still might be useful info!

did you solve it?

what was your pool and special device sizes?

what was your special_small_blocks setting?

can you show us output of this command?

find . -type f -print0 | xargs -0 ls -l | awk '{ n=int(log($5)/log(2)); if (n<10) { n=10; } size[n]++ } END { for (i in size) printf("%d %d\n", 2^i, size[i]) }' | sort -n | awk 'function human(x) { x[1]/=1024; if (x[1]>=1024) { x[2]++; human(x) } } { a[1]=$1; a[2]=0; human(a); printf("%3d%s: %6d\n", a[1],substr("kMGTEPYZ",a[2]+1,1),$2) }'