Btrfs raid1 "full sized"?

Btrfs raid1 "full sized"?

[Claes Gyllenswärd]

I've tried setting up a raid1 on two drives like this:

mkfs.btrfs -m raid1 -d raid1 /dev/sdb /dev/sdc

Then I copy my old install onto the new drives, and check the drives' status:

# mount | grep "on / "
/dev/sdb on / type btrfs (rw,noatime)
# btrfs fi df /
Data, RAID1: total=259.00GB, used=256.64GB
Data: total=8.00MB, used=0.00
System, RAID1: total=8.00MB, used=44.00KB
System: total=4.00MB, used=0.00
Metadata, RAID1: total=4.50GB, used=1.27GB
Metadata: total=8.00MB, used=0.00
# btrfs fi show
Label: none  uuid: c6c89292-ea29-484c-ad29-9003a5fedf90
        Total devices 2 FS bytes used 257.93GB
        devid    1 size 931.51GB used 263.53GB path /dev/sdb
        devid    2 size 931.51GB used 263.51GB path /dev/sdc

Label: none  uuid: 6f2f8317-3012-4e79-a82d-ab2e8eaa6cd6
        Total devices 1 FS bytes used 354.99GB
        devid    1 size 465.65GB used 465.65GB path /dev/sda2

My interpretation of the above data is that /dev/sdb and /dev/sdc are
exact mirrors of each other, and contain my / root partition.

This would make complete sense if it wasn't for the fact that I've
copied all the data from /dev/sda2 onto /dev/sdb. From the information
above, it looks like the data has been split like in raid-0, instead
of the what I expect, mirrored like in raid-1.

I tried reading the FAQ about "Why are there so many ways to check the
amount of free space?" hoping this would make it more clear, but it
doesn't. Can anyone tell me what's going on?

I found one thread with a similar question that went unanswered, and
it was also back in 2008 so the answer might differ quite a bit
anyway.

Re: Btrfs raid1 "full sized"?

[cwillu]

On Sun, May 1, 2011 at 12:33 PM, Claes Gyllensw=C3=A4rd <letharion@gmai=
l.com> wrote:
> I've tried setting up a raid1 on two drives like this:
>
> mkfs.btrfs -m raid1 -d raid1 /dev/sdb /dev/sdc
>
> Then I copy my old install onto the new drives, and check the drives'=
 status:
>
> # mount | grep "on / "
> /dev/sdb on / type btrfs (rw,noatime)
> # btrfs fi df /
> Data, RAID1: total=3D259.00GB, used=3D256.64GB
> Data: total=3D8.00MB, used=3D0.00
> System, RAID1: total=3D8.00MB, used=3D44.00KB
> System: total=3D4.00MB, used=3D0.00
> Metadata, RAID1: total=3D4.50GB, used=3D1.27GB
> Metadata: total=3D8.00MB, used=3D0.00
> # btrfs fi show
> Label: none =C2=A0uuid: c6c89292-ea29-484c-ad29-9003a5fedf90
> =C2=A0 =C2=A0 =C2=A0 =C2=A0Total devices 2 FS bytes used 257.93GB
> =C2=A0 =C2=A0 =C2=A0 =C2=A0devid =C2=A0 =C2=A01 size 931.51GB used 26=
3.53GB path /dev/sdb
> =C2=A0 =C2=A0 =C2=A0 =C2=A0devid =C2=A0 =C2=A02 size 931.51GB used 26=
3.51GB path /dev/sdc
>
> Label: none =C2=A0uuid: 6f2f8317-3012-4e79-a82d-ab2e8eaa6cd6
> =C2=A0 =C2=A0 =C2=A0 =C2=A0Total devices 1 FS bytes used 354.99GB
> =C2=A0 =C2=A0 =C2=A0 =C2=A0devid =C2=A0 =C2=A01 size 465.65GB used 46=
5.65GB path /dev/sda2
>
> My interpretation of the above data is that /dev/sdb and /dev/sdc are
> exact mirrors of each other, and contain my / root partition.
>
> This would make complete sense if it wasn't for the fact that I've
> copied all the data from /dev/sda2 onto /dev/sdb. From the informatio=
n
> above, it looks like the data has been split like in raid-0, instead
> of the what I expect, mirrored like in raid-1.
>
> I tried reading the FAQ about "Why are there so many ways to check th=
e
> amount of free space?" hoping this would make it more clear, but it
> doesn't. Can anyone tell me what's going on?
>
> I found one thread with a similar question that went unanswered, and
> it was also back in 2008 so the answer might differ quite a bit
> anyway.

How did you copy it exactly?  I see 100gb missing, which makes me
wonder if you maybe had subvolumes on sdb, and used the -x option to
rsync or similar:  subvolumes count as different mounts for the
purposes of --one-file-system'like options.

Can you provide the df -h output for both filesystems, as well as the
btrfs fi df for /dev/sda2?
The total reported by du -sh for each would be useful as well as a sani=
ty check.
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Re: Btrfs raid1 "full sized"?

[Claes Gyllenswärd]

2011/5/1 cwillu <cwillu@cwillu.com>:
> On Sun, May 1, 2011 at 12:33 PM, Claes Gyllensw=C3=A4rd <letharion@gm=
ail.com> wrote:
>> I've tried setting up a raid1 on two drives like this:
>>
>> mkfs.btrfs -m raid1 -d raid1 /dev/sdb /dev/sdc
>>
>> Then I copy my old install onto the new drives, and check the drives=
' status:
>>
>> # mount | grep "on / "
>> /dev/sdb on / type btrfs (rw,noatime)
>> # btrfs fi df /
>> Data, RAID1: total=3D259.00GB, used=3D256.64GB
>> Data: total=3D8.00MB, used=3D0.00
>> System, RAID1: total=3D8.00MB, used=3D44.00KB
>> System: total=3D4.00MB, used=3D0.00
>> Metadata, RAID1: total=3D4.50GB, used=3D1.27GB
>> Metadata: total=3D8.00MB, used=3D0.00
>> # btrfs fi show
>> Label: none =C2=A0uuid: c6c89292-ea29-484c-ad29-9003a5fedf90
>> =C2=A0 =C2=A0 =C2=A0 =C2=A0Total devices 2 FS bytes used 257.93GB
>> =C2=A0 =C2=A0 =C2=A0 =C2=A0devid =C2=A0 =C2=A01 size 931.51GB used 2=
63.53GB path /dev/sdb
>> =C2=A0 =C2=A0 =C2=A0 =C2=A0devid =C2=A0 =C2=A02 size 931.51GB used 2=
63.51GB path /dev/sdc
>>
>> Label: none =C2=A0uuid: 6f2f8317-3012-4e79-a82d-ab2e8eaa6cd6
>> =C2=A0 =C2=A0 =C2=A0 =C2=A0Total devices 1 FS bytes used 354.99GB
>> =C2=A0 =C2=A0 =C2=A0 =C2=A0devid =C2=A0 =C2=A01 size 465.65GB used 4=
65.65GB path /dev/sda2
>>
>> My interpretation of the above data is that /dev/sdb and /dev/sdc ar=
e
>> exact mirrors of each other, and contain my / root partition.
>>
>> This would make complete sense if it wasn't for the fact that I've
>> copied all the data from /dev/sda2 onto /dev/sdb. From the informati=
on
>> above, it looks like the data has been split like in raid-0, instead
>> of the what I expect, mirrored like in raid-1.
>>
>> I tried reading the FAQ about "Why are there so many ways to check t=
he
>> amount of free space?" hoping this would make it more clear, but it
>> doesn't. Can anyone tell me what's going on?
>>
>> I found one thread with a similar question that went unanswered, and
>> it was also back in 2008 so the answer might differ quite a bit
>> anyway.
>
> How did you copy it exactly? =C2=A0I see 100gb missing, which makes m=
e
> wonder if you maybe had subvolumes on sdb, and used the -x option to
> rsync or similar: =C2=A0subvolumes count as different mounts for the
> purposes of --one-file-system'like options.
>
> Can you provide the df -h output for both filesystems, as well as the
> btrfs fi df for /dev/sda2?
> The total reported by du -sh for each would be useful as well as a sa=
nity check.
>

My apologies, it appears that I've made a mistake and mixed up my numbe=
rs.
Your remark that I was missing 100gb made me re reformat the raid and
copy over my data again.
This time everything looks as expected. Thank you for your time.
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