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).
Hugo.
d=data
m=metadata
.=unusable
{ 500mb} [|ddddd|] /dev/sda1
{ 3000mb} [|ddddd|mmmmm|mmmmm|mmmmm|mmmmm|mm...|] /dev/sdb1
{ 3000mb} [|ddddd|mmmmm|mmmmm|mmmmm|mmmmm|mmm..|] /dev/sdc2
{ 5000mb}
[|ddddd|mmmmm|mmmmm|mmmmm|mmmmm|mmmmm|mmmmm|mmmmm|mmmmm|mmmmm|]
/dev/sdb1
--------
{11500mb} Total space
usable for data (raid10): 1000mb / 2000mb
usable for metadata (raid1): 4500mb / 9000mb
unusable: 500mb
Of course this would have to change one (if ever) subvolumes can
have different raid levels etc, but I would have loved using
something like this instead of jumping around carfax abbey (!) at
night.
The core algorithm for the tool actually works pretty well for
dealing with different RAID levels, as long as you know how much of
each kind of data you're going to be using. (Although it's actually
path-dependent -- write 100 GB of RAID-0 then 100 GB of RAID-1 can
have different results than if you write them in the opposite order --
but that's a kind of edge effect).
Hugo.
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