Re: btrfs raid assurance

["Austin S. Hemmelgarn" <ahferroin7@gmail.com>]

On 2017-07-26 08:27, Hugo Mills wrote:
> On Wed, Jul 26, 2017 at 08:12:19AM -0400, Austin S. Hemmelgarn wrote:
>> On 2017-07-25 17:45, Hugo Mills wrote:
>>> On Tue, Jul 25, 2017 at 11:29:13PM +0200, waxhead wrote:
>>>>
>>>>
>>>> Hugo Mills wrote:
>>>>>
>>>>>>>     You can see about the disk usage in different scenarios with the
>>>>>>> online tool at:
>>>>>>>
>>>>>>> http://carfax.org.uk/btrfs-usage/
>>>>>>>
>>>>>>>     Hugo.
>>>>>>>
>>>> As a side note, have you ever considered making this online tool
>>>> (that should never go away just for the record) part of btrfs-progs
>>>> e.g. a proper tool? I use it quite often (at least several timers
>>>> per. month) and I would love for this to be a visual tool
>>>> 'btrfs-space-calculator' would be a great name for it I think.
>>>>
>>>> Imagine how nice it would be to run....
>>>>
>>>> btrfs-space-calculator -mraid1 -draid10 /dev/sda1 /dev/sdb1
>>>> /dev/sdc2 /dev/sdd2 /dev/sde3 for example and instantly get
>>>> something similar to my example below (no accuracy intended)
>>>
>>>     It's certainly a thought. I've already got the algorithm written
>>> up. I'd have to resurrect my C skills, though, and it's a long way
>>> down my list of things to do. :/
>>>
>>>     Also on the subject of this tool, I'd like to make it so that the
>>> parameters get set in the URL, so that people can copy-paste the URL
>>> of the settings they've got into IRC for discussion. However, that
>>> would involve doing more JavaScript, which is possibly even lower down
>>> my list of things to do than starting doing C again...
> 
>> Is the core logic posted somewhere?  Because if I have some time, I
>> might write up a quick Python script to do this locally (it may not
>> be as tightly integrated with the regular tools, but I can count on
>> half a hand how many distros don't include Python by default).
> 
>     If it's going to be done in python, I might as well do it myself --
> I can do python with my eyes closed. It's just C and JS I'm rusty with.
Same here ironically :)
> 
>     There is a write-up of the usable-space algorithm somewhere. I
> wrote it up in detail (with pseudocode) in a mail on this list. I've
> also got several pages of LaTeX somewhere where I tried and failed to
> prove the correctness of the formula. I'll see if I can dig them out
> this evening.
It looks like the Message-ID for the one on the mailing list is 
<20160311221703.GJ17196@carfax.org.uk>
I had forgotten that I'd archived that with the intent of actually doing 
something with it eventually...