Hi!
I've read the explanation about how much space is available using disks
with different sizes[1]. I understand the rules, but I see a contradiction
with definition of RAID-1 in btrs:
«A form of *RAID* which stores two complete copies of each piece of data.
Each copy is stored on a different *device*. btrfs requires a minimum of
two devices to use RAID-1. This is the default for btrfs's *metadata* on
more than one device.
So, let's say we have 3 small disks: 4GB, 3G, and 2GB.
If I create one file of 3GB I think that
3 GB is written on 4GB disk, it leaves 1 GB free.
3 GB of copy is written on 3 GB disk, it leaves 0 GB Free.
So, I create one file of 1GB that is written on 4GB disk, it leaves 0 GB
free.
1 GB of copy is written on 2 GB disk, so it leaves 1 GB free.
So I've used 4GB, ok it leaves 1 GB free on only one disk, but cannot be
mirrored.
However as [1] I could use 4.5 ((4GB+3GB+2GB)/2) GB instead of 4GB. Surely,
I'm missing or mistaking something.
Please could you help me?
[1]:
https://btrfs.wiki.kernel.org/index.php/FAQ#How_much_space_do_I_get_with_...
[2]:
https://btrfs.wiki.kernel.org/index.php/Glossary
Thanks in advance!
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Sergio Belkin
LPIC-2 Certified -
http://www.lpi.org