setup raidz2 with mix drives

[T_T]

Hello all,
So I am currently have 8x4tb drives and 2x5tb drives. I ordered them all at 4tb but the person that shipped the products got mixed up and now I can't return the drives. I do not need or want to use the 2 tb extra that I got from the 2x5tb. I am setting up a raidZ2 array which I think freenas will take out only 2 drives. So I should get at least 29TB. However, I ended up with only 26.7TB.

• Can anybody explain to my why this is the case? My theory is that it has to do with the 5tb drives somehow.
• I think normally if I want to expand my pool then I can just replace each individual drive with a bigger drive (this does not have to be at the same time, but I won't get the full capacity until all the drives are replaced with a bigger size?). But in my case, I'm trying to the opposite. Can I later on replace the 5tb drives with the 4tb, and will I get any storage in additional to the 26.7TB from having all drives the same size?

 

[Alecmascot]

Sounds about right : https://wintelguy.com/zfs-calc.pl

You may not be able to swap the 5tb out for 4tb.
Perhaps someone who has tried will be along soon......

 

[T_T]

Sounds about right : https://wintelguy.com/zfs-calc.pl

You may not be able to swap the 5tb out for 4tb.
Perhaps someone who has tried will be along soon......

So what happen if have the system running and switch out the 5tb to the 4tb?

 

[T_T]

Sounds about right : https://wintelguy.com/zfs-calc.pl

You may not be able to swap the 5tb out for 4tb.
Perhaps someone who has tried will be along soon......

I believe I found the answer here https://www.ixsystems.com/community/threads/replacing-a-non-full-disk-with-a-smaller-disk.54130/
Still not sure tho !!
If anybody can give me a confirmation. That would be great

 

[Alecmascot]

Well there you go...it can be done.

 

[pschatz100]

You will not get any diffferent usable capacity by switching out the 5TB drives for 4TB drives. Keep the 5TB drives... their larger size does not matter.

You are confusing the measurement units of TB, which hard drive manufacturers use, with TiB which enterprise IT people use and is the measurement unit that FreeNAS reports. At the end of the day, you do not have 26.7 TB, you have 26.7 TiB of usable space - which is appropriate for your configuration. You are OK.

This mix up of measurement units is very confusing until you understand better. You can do an internet search to learn more about the differences.

 

[T_T]

You will not get any diffferent usable capacity by switching out the 5TB drives for 4TB drives. Keep the 5TB drives... their larger size does not matter.

You are confusing the measurement units of TB, which hard drive manufacturers use, with TiB which enterprise IT people use and is the measurement unit that FreeNAS reports. At the end of the day, you do not have 26.7 TB, you have 26.7 TiB of usable space - which is appropriate for your configuration. You are OK.

This mix up of measurement units is very confusing until you understand better. You can do an internet search to learn more about the differences.

Thank you so much for the clarification. That’s why before the upgrade to 11.3U3.2. I was very certain I saw 29 TB (Terabyte). But then now Freenas display using a different Unit which is TiB (Tebibyte). I did a conversion on google and sure enough. 26.7 TiB ~ 29.35 TB.