6 TB Drives Raidz2 only 7.1 usable?

[Miniwehats]

Can someone clarify for me here I have 6 2tb drives in Raidz2 and I was under the impression that would give me 8tb volume but it is coming up with 7.1 volume size. I factory reset the NAS and tried again and have tried from 2 different browsers.

 

[toddos]

It's math. 2TB in drive manufacturer terms == 1.8TB in real terms (2x10^12 vs. 2x2^40). So 4 x 1.8TB = 7.2TB. Subtract 2GB per drive for swap, various other overhead, etc, and you end up with 7.1TB.

 

[Middling]

FreeNAS is incorrectly using TB in the GUI when they mean TiB.

Your 8TB is there (minus the swap and overhead as toddos says), it's FreeNAS's reporting that's causing the confusion and should be fixed to either use TiB or (more properly) report proper decimal disk sizes.

 

[toddos]

FreeNAS is incorrectly using TB in the GUI when they mean TiB.

Your 8TB is there (minus the swap and overhead as toddos says), it's FreeNAS's reporting that's causing the confusion and should be fixed to either use TiB or (more properly) report proper decimal disk sizes.

FreeNAS isn't doing anything that most other OSes do. TB for base-2 is well-accepted, even though as you point out it's not technically a standard. But then "tebi" is not an SI standard, either. Even if FreeNAS used "TiB", this question would still come up all the time because people in general do not distinguish between TB and TiB despite their base differences. I've literally never heard anybody say "tebibyte" in real life.

 

[Middling]

You're right that most other OSs also do this incorrectly, but i don't think that's a valid reason for FreeNAS to also display storage sizes incorrectly.

It seems that FreeNAS is actually using TiB in some places in the GUI and TB in others, even though it means TiB for both. In "Settings/Advanced" it uses GiB, and in "Storage" it uses TiB, but in "Reporting/Diskspace" it uses TB.

So long as it's consistent across the board, and uses the proper unit, i don't really care all that much whether FreeNAS uses binary TiB or decimal TB. I do think that using decimal TB would be better though because, with the massive array sizes FreeNAS supports, the difference between perceived sizes are becoming huge and, as you say, most people don't distinguish between TiB and TB.

 

[toddos]

Operating systems don't report sizes in base-10, so converting everything to base-10 for reporting would be silly. That said, I agree with you that FreeNAS should be consistent in is units. It should either always be TB or always be TiB, not a mixture of both. Maybe file a bug?

 

[JaimieV]

OSX uses base-10 for disk sizes, since 10.6.

 

[paleoN]

That said, I agree with you that FreeNAS should be consistent in is units.

Consistency is desirable, TiB is not.

I do think that using decimal TB would be better though because, with the massive array sizes FreeNAS supports, the difference between perceived sizes are becoming huge and, as you say, most people don't distinguish between TiB and TB.

Except, this is common knowledge and yes I realize everyone doesn't know it. If everyone knew perhaps the marketing would change and no I don't actually believe that.

 

[cyberjock]

The whole battle between TB and TiB was ENTIRELY brought on by hard drive marketing. MB/GB/TB had always been base-2. When they got their butts sued for using base 10(because its smaller than the base-2 formula) they pushed for the IEEE standard(or whatever standard it was) to make TB base-10 and TiB base-2(after 50+ years of computing where TB was base-2 and there was no TiB OR base-10 standard).

COMPLETE AND UTTER BS. I will never recognize TiB as a valid size and I will ALWAYS expect TB from hard drive manufacturers to be base-10 while everything else is base-2.