Re: Size reported differently between profiles

[Andrei Borzenkov <arvidjaar@gmail.com>]

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17.07.2016 05:09, Sébastien Luttringer пишет:
> Hello,
> 
> «btrfs fi usage» report size differently between single,RAID0,RAID1,RAID5,RAID6
> and RAID10.
> 
> The test is done with 2 files of 1.4GiB each on 4x10GiB devices. I used balance
> to get size between profiles.
> 
> Data,single: Size:4.00GiB, Used:2.85GiB
>    /dev/sdb	   1.00GiB
>    /dev/sdc	   1.00GiB
>    /dev/sdd	   1.00GiB
>    /dev/sde	   1.00GiB
> 
> Data,RAID0: Size:8.00GiB, Used:2.85GiB
>    /dev/sdb	   2.00GiB
>    /dev/sdc	   2.00GiB
>    /dev/sdd	   2.00GiB
>    /dev/sde	   2.00GiB
> 
> Data,RAID1: Size:4.00GiB, Used:2.85GiB
>    /dev/sdb	   2.00GiB
>    /dev/sdc	   2.00GiB
>    /dev/sdd	   2.00GiB
>    /dev/sde	   2.00GiB
> 
> Data,RAID5: Size:6.00GiB, Used:2.85GiB
>    /dev/sdb	   2.00GiB
>    /dev/sdc	   2.00GiB
>    /dev/sdd	   2.00GiB
>    /dev/sde	   2.00GiB
> 
> Data,RAID6: Size:6.00GiB, Used:2.85GiB
>    /dev/sdb	   3.00GiB
>    /dev/sdc	   3.00GiB
>    /dev/sdd	   3.00GiB
>    /dev/sde	   3.00GiB
> 
> Data,RAID10: Size:4.00GiB, Used:2.85GiB
>    /dev/sdb	   1.00GiB
>    /dev/sdc	   1.00GiB
>    /dev/sdd	   1.00GiB
>    /dev/sde	   1.00GiB
> 
> For single,RAID0,RAID10 profiles, the sum of device sizes is equal to
> total size. Like total size is the "byte allocated size" for all
> devices.
> 
> For RAID1,RAID5,RAID6 profiles, sum of devices sizes is more than the
> total size. Looks like the redundancy was subtracted from the total. 
> Like total size is the "profile size allocated".
> 
> So, why RAID1 and RAID10 are reporting their sizes differently? This
> confuse me.
> 

In your example only RAID10 is different. RAID1 shows 4GiB on 8GiB total
disks which matches "redundancy subtracted". But yes, I also wonder why
RAID10 does not respect it.


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