On 16.07.2018 23:58, Wolf wrote:
> Greetings,
> I would like to ask what what is healthy amount of free space to keep on
> each device for btrfs to be happy?
>
> This is how my disk array currently looks like
>
> [root@dennas ~]# btrfs fi usage /raid
> Overall:
> Device size: 29.11TiB
> Device allocated: 21.26TiB
> Device unallocated: 7.85TiB
> Device missing: 0.00B
> Used: 21.18TiB
> Free (estimated): 3.96TiB (min: 3.96TiB)
> Data ratio: 2.00
> Metadata ratio: 2.00
> Global reserve: 512.00MiB (used: 0.00B)
>
> Data,RAID1: Size:10.61TiB, Used:10.58TiB
> /dev/mapper/data1 1.75TiB
> /dev/mapper/data2 1.75TiB
> /dev/mapper/data3 856.00GiB
> /dev/mapper/data4 856.00GiB
> /dev/mapper/data5 1.75TiB
> /dev/mapper/data6 1.75TiB
> /dev/mapper/data7 6.29TiB
> /dev/mapper/data8 6.29TiB
>
> Metadata,RAID1: Size:15.00GiB, Used:13.00GiB
> /dev/mapper/data1 2.00GiB
> /dev/mapper/data2 3.00GiB
> /dev/mapper/data3 1.00GiB
> /dev/mapper/data4 1.00GiB
> /dev/mapper/data5 3.00GiB
> /dev/mapper/data6 1.00GiB
> /dev/mapper/data7 9.00GiB
> /dev/mapper/data8 10.00GiB
>
> System,RAID1: Size:64.00MiB, Used:1.50MiB
> /dev/mapper/data2 32.00MiB
> /dev/mapper/data6 32.00MiB
> /dev/mapper/data7 32.00MiB
> /dev/mapper/data8 32.00MiB
>
> Unallocated:
> /dev/mapper/data1 1004.52GiB
> /dev/mapper/data2 1004.49GiB
> /dev/mapper/data3 1006.01GiB
> /dev/mapper/data4 1006.01GiB
> /dev/mapper/data5 1004.52GiB
> /dev/mapper/data6 1004.49GiB
> /dev/mapper/data7 1005.00GiB
> /dev/mapper/data8 1005.00GiB
>
> Btrfs does quite good job of evenly using space on all devices. No, how
> low can I let that go? In other words, with how much space
> free/unallocated remaining space should I consider adding new disk?
Btrfs will start running into problems when you run out of unallocated
space. So the best advice will be monitor your device unallocated, once
it gets really low - like 2-3 gb I will suggest you run balance which
will try to free up unallocated space by rewriting data more compactly
into sparsely populated block groups. If after running balance you
haven't really freed any space then you should consider adding a new
drive and running balance to even out the spread of data/metadata.
>
> Thanks for advice :)
>
> W.
>
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
