question about zpool and dataset size delta

[denut]

hello

i have a question about the size my pool (1.9TiB) and my dataset only 1.4TiB

why this difference of 192GiB

tank's

 

[depasseg]

Parity and possibly snapshots.

 

[denut]

snapshot i thick no

but parity maybe but i dont understand something

i have 16x149GiB driver in raidz3 this give me a 2.38TiB pool minus 3 drives total 1.9Tib size of my volume all is ok

i create a dataset and then the size is now only 1.7Tib

where are this 200GiB

my question was incomplete, thank's for you fast reply :)

 

[depasseg]

the first line is the raw size
the second line is the size after parity and file system structure.
Are you sure your disks are 149GiB, or are they 149GB? There is a ~10% difference between those terms.

 

[denut]

GiB i convert the commercial size of 160GB to the real size

 

[depasseg]

OK. Then there is 2GB swap on each drive and there is ZFS metadata on each disk.

Normally I'd point people to @Bidule0hm zfs sizing page, but I'm not sure his drive calculator handles sub-TB drives. I tried entering .160TB
https://jsfiddle.net/Biduleohm/paq5u7z5/1/embedded/result/

 

[denut]

thank's

i enter 0.160GB
result in picture 1.892 TiB but I have 1.7

 

[denut]

maybe i have a idea

i'm not using only 160GB drives but a mix because I don't have all my new drives (i have considerate all drives like the smaller)

there is some 160GB some 250GB, 500GB, 1TB, 1.5TB, and 2TB

is it possible due to drives with 4k sectors and other not ?

 

[denut]

at end all drives will be 2TB

and my problem is to be sure at end with my all 2TB drives i will not lost exponentially the difference i see at this point

 

[Bidule0hm]

but I'm not sure his drive calculator handles sub-TB drives.

Yes it does, just enter 0.xxx ;)

result in picture 1.892 TiB but I have 1.7

That's probably because the misalignment overhead isn't computed for now. https://forums.freenas.org/index.php?threads/misaligned-pools-and-lost-space.40288/

 

[denut]

ok tank's i read this tomorrow or after tomorrow , too tired tonight and i give you feedback :)

 

[denut]

hello

i look on my pool and the ashift is to 12

most of my drives are not 4k but 512b this if why i lost space .... (if i understand goo the link https://forums.freenas.org/index.php?threads/misaligned-pools-and-lost-space.40288/)

is there a way to change this value without recreate the pool ?

and for the future return to this value

 

[denut]

or change the record size value ?

 

[denut]

and if i need recreate the pool what is the best ashift (or and) record size value for a raidz3 16 hdd (video and VM storage)

tank's

 

[denut]

and is it a command to check what drive is native a 4k or 512b ?

EDIT:
i found a command : fdisk -itv /dev/da12 answers no at the first question and report the sector size

all of my drive show 512b ...

after i found a list of 4096b drives but all have physically 4096b but logically 512b
https://wiki.archlinux.org/index.php/Advanced_Format

then if most of drives are logically 512b why freenas set a default ashift to 12 and not 9 ?

is my controller and or back plane not 4096b compatible ,Supermicro BPN-SAS-836EL1 16 Hotswap, LSI sas 9211-8i 6 Gbits/s 8 ports sas ?

many question !!!!

 

[Bidule0hm]

Actually there's no real harm (no lost space, maybe a little bit of perfs loss) to use 4 kB blocks on 512 B sectors drives.

It's the physical value that matters here. The logical 512 B is only for compatibility.

What are the models of your drives?

 

[denut]

A lot of different drives some wd20ears wd20earx segate constellation 2tb and smaller 500gb Samsung and western digital

Total 16 drives in raidz3


At beginning I was working with a 160gb for the smallest drive and the delta was 200gb

Now the smallest is 320gb and the delta have grow to 800gb

I need to understand why because after changing my last drive to a 2tb the delta will be dramatically enormous and if I need to recreate the pool I must now how before I have to many data inside....

 

[denut]

next test :

i have recreated my pool on vmware workstation with the same drive size the pool was set automatically to ashift=9 and there is no delta

my pool with ashift= 12 400Gb delta (on the total pool) and 800GB on free space .....

then i'm will try to recreate my pool

if any one have solution to change this value without recreate i need it :)

 

[Bidule0hm]

At least the WD20EARX should be a 4 kB sector drive.

i have recreated my pool on vmware workstation with the same drive size the pool was set automatically to ashift=9 and there is no delta

Yep, already told you that in the previous post.

 

[denut]

can you give me the command to create the pool with ashift=9 and mixed drives size

because all i try don't work
"zpool create -f -O ashift=9 -m /mnt/v16d v16d raidz3 ada1 ada2 ada3 ada4 ada5 ada6 ada7 ada8 ada9 ada10 ada11 ada12 ada13 ada14 ada15 ada16"

and by simple creation the pool is not visible in the web interface...

tank's