ZFS Drive Size and Cost Comparison Spreadsheet

[diedrichg]

@diedrichg Question: in cell E105, why do you say that for 2-way mirrored 4TB drives, you get 2.86TB of usable space? Shouldn't that be 3.86TB? That, or something pretty close to that, is the number that I remember FreeNAS 11's GUI told me I had when I configured my 1 set of 2-way mirrored 4TB pool (i.e. 8TB/2 - swap space).

You are partly correct; 3.86 (give-or-take) is the raw size where 2.86TiB would be the usable space per Bidule0hm 's ZFS RAID Size Calculator.

 

[Juan Manuel Palacios]

Yeah, I was reviewing it, but I still don't understand, because if it weren't for the swap space I'd have a full 4TB of usable space in my single set of 2-way mirrored 4TB drives pool. But, because of the swap space, I have a little less than 4TB, exactly 3.62TB according to 'zpool list' (which, I believe, is also what the GUI said before I copied data into my pool), so I don't understand where that missing 1TB in the spreadsheet is going...

 

[diedrichg]

Yeah, I was reviewing it, but I still don't understand, because if it weren't for the swap space I'd have a full 4TB of usable space in my single set of 2-way mirrored 4TB drives pool. But, because of the swap space, I have a little less than 4TB, exactly 3.62TB according to 'zpool list' (which, I believe, is also what the GUI said before I copied data into my pool), so I don't understand where that missing 1TB in the spreadsheet is going...

You aren't taking into account that ZFS drastically slows down when the pool is >80% capacity. The calculator takes this into account and subtracts the 20% reserve space from your usable space available. That comes out to about 700GiB that you should not use to keep your pool healthy and running at full speed.

 

[Bidule0hm]

First we need to know if we talk about TB or TiB because they're not the same: 4 TB = 3.638 TiB.

Then the explanation is very simple: there's about 0.06 TiB of metadata (used by ZFS, you can't use that space for your data) and the rest (about 0.72 TiB) is the 20 % recommended free space (crossing the 80 % used space limit is a sign you should do something about and crossing the 90 % limit is a bad idea for perfs).

 

[joeschmuck]

Then the explanation is very simple:

I love the simple stuff ;)

 

[patrick sullivan]

awesome....thank yee!!!!

 

[diedrichg]

It has been awhile since I've bumped my own thread. No changes other than throwing in current prices in the online spreadsheet, there is a downloadable one too.

 

[diedrichg]

Well. It was brought to my attention that the previous offline file did not have any formulas! I just assumed you could export from Google Sheets to xlsx and everything would copy over correctly. So much for proofreading my own work! All is fixed now, both online and offline versions have been checked for accuracy.

 

[Chris Moore]

I am just seeing this and have not looked enough yet, but is it related to this:

Disk Price/Performance Analysis Buying Information
https://forums.freenas.org/index.ph...e-performance-analysis-buying-information.62/

 

[diedrichg]

I am just seeing this and have not looked enough yet, but is it related to this:

Disk Price/Performance Analysis Buying Information
https://forums.freenas.org/index.ph...e-performance-analysis-buying-information.62/

No. Mine was created 1yr/4mo earlier and based on Bidule0hm's calculator which is 1yr/11mo older. The one you linked is a nice spreadsheet but mine is quite different. Mine has the ability to optimize your purchase decision for drive cost and pool size. I've wanted to get it in the resource section but haven't had any luck getting the admins to move it. I guess I could spend a few minutes and create a new resource thread.

 

[Chris Moore]

I guess I could spend a few minutes and create a new resource thread.

It might make this easier for anyone to find, if you have the time.