How to remove a device on a RAID-1 before replacing it?

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* How to remove a device on a RAID-1 before replacing it?
@ 2011-03-29 20:09 Andrew Lutomirski
  2011-03-29 20:21 ` cwillu
  0 siblings, 1 reply; 5+ messages in thread
From: Andrew Lutomirski @ 2011-03-29 20:09 UTC (permalink / raw)
  To: linux-btrfs

I have a disk with a SMART failure.  It still works but I assume it'll
fail sooner or later.

I want to remove it from my btrfs volume, replace it, and add the new
one.  But the obvious command doesn't work:

# btrfs device delete /dev/dm-5 /mnt/foo
ERROR: error removing the device '/dev/dm-5'

dmesg says:
btrfs: unable to go below two devices on raid1

With mdadm, I would fail the device, remove it, run degraded until I
get a new device, and hot-add that device.

With btrfs, I'd like some confirmation from the fs that data is
balanced appropriately so I won't get data loss if I just yank the
drive.  And I don't even know how to tell btrfs to release the drive
so I can safely remove it.

(Mounting with -o degraded doesn't help.  I could umount, remove the
disk, then remount, but that feels like a hack.)

This is 2.6.38.1 running Fedora 14's version of btrfs-progs, but
btrfs-progs-unstable git does the same thing, as does btrfs-vol -r.

--Andy

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: How to remove a device on a RAID-1 before replacing it?
  2011-03-29 20:09 How to remove a device on a RAID-1 before replacing it? Andrew Lutomirski
@ 2011-03-29 20:21 ` cwillu
  2011-03-29 20:45   ` Helmut Hullen
  2011-03-29 21:01   ` Andrew Lutomirski
  0 siblings, 2 replies; 5+ messages in thread
From: cwillu @ 2011-03-29 20:21 UTC (permalink / raw)
  To: Andrew Lutomirski; +Cc: linux-btrfs

On Tue, Mar 29, 2011 at 2:09 PM, Andrew Lutomirski <luto@mit.edu> wrote=
:
> I have a disk with a SMART failure. =A0It still works but I assume it=
'll
> fail sooner or later.
>
> I want to remove it from my btrfs volume, replace it, and add the new
> one. =A0But the obvious command doesn't work:
>
> # btrfs device delete /dev/dm-5 /mnt/foo
> ERROR: error removing the device '/dev/dm-5'
>
> dmesg says:
> btrfs: unable to go below two devices on raid1
>
> With mdadm, I would fail the device, remove it, run degraded until I
> get a new device, and hot-add that device.
>
> With btrfs, I'd like some confirmation from the fs that data is
> balanced appropriately so I won't get data loss if I just yank the
> drive. =A0And I don't even know how to tell btrfs to release the driv=
e
> so I can safely remove it.
>
> (Mounting with -o degraded doesn't help. =A0I could umount, remove th=
e
> disk, then remount, but that feels like a hack.)

There's no "nice" way to remove a failing disk in btrfs right now
("btrfs dev delete" is more of a online management thing to politely
remove a perfectly functional disk you'd like to use for something
else.)  As I understand things, the only way to do it right now is the
umount, remove disk, remount w/ degraded, and then btrfs add the new
device.
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* Re: How to remove a device on a RAID-1 before replacing it?
  2011-03-29 20:21 ` cwillu
@ 2011-03-29 20:45   ` Helmut Hullen
  2011-03-29 21:01   ` Andrew Lutomirski
  1 sibling, 0 replies; 5+ messages in thread
From: Helmut Hullen @ 2011-03-29 20:45 UTC (permalink / raw)
  To: linux-btrfs

Hallo, cwillu,

Du meintest am 29.03.11:

>> I have a disk with a SMART failure. =A0It still works but I assume
>> it'll fail sooner or later.
>>
>> I want to remove it from my btrfs volume, replace it, and add the
>> new one. =A0But the obvious command doesn't work:

[...]


> There's no "nice" way to remove a failing disk in btrfs right now
> ("btrfs dev delete" is more of a online management thing to politely
> remove a perfectly functional disk you'd like to use for something
> else.)

Nice hope, but even "btrfs device delete /dev/sdxn /mnt/btr" doesn't  =20
work well.

I've tried it, with kernel 2.6.38.1 ...

# mkfs.btrfs -L SCSI -m raid0 /dev/sda1
# mount LABEL=3DSCSI /mnt/btr

# btrfs filesystem show
Label: 'SCSI'  uuid: 4d834705-5a65-4d1f-a8a0-a5ea9348db50
	Total devices 1 FS bytes used 28.00KB
	devid    1 size 4.04GB used 20.00MB path /dev/sda1

Btrfs Btrfs v0.19

# btrfs filesystem df /mnt/btr
Data: total=3D8.00MB, used=3D0.00
System: total=3D4.00MB, used=3D8.00KB
Metadata: total=3D8.00MB, used=3D20.00KB

# df -t btrfs
=46ilesystem    Type   1K-blocks      Used Available Use% Mounted on
/dev/sda1    btrfs     4232556        28   4220224   1% /mnt/btr

# gdisk -l
/dev/sda
   1            2048         8467166   4.0 GiB     0700  Linux/Windows =
data
#------------------------------------------------------------
# btrfs device add /dev/sdc1 /mnt/btr

# btrfs filesystem show
Label: 'SCSI'  uuid: 4d834705-5a65-4d1f-a8a0-a5ea9348db50
	Total devices 2 FS bytes used 28.00KB
	devid    1 size 4.04GB used 433.31MB path /dev/sda1
	devid    2 size 8.54GB used 0.00 path /dev/sdc1

Btrfs Btrfs v0.19

# btrfs filesystem df /mnt/btr
Data: total=3D421.31MB, used=3D0.00
System: total=3D4.00MB, used=3D4.00KB
Metadata: total=3D8.00MB, used=3D24.00KB

# df -t btrfs
=46ilesystem    Type   1K-blocks      Used Available Use% Mounted on
/dev/sda1    btrfs    13189632        28  13176256   1% /mnt/btr

# gdisk -l
/dev/sda
   1            2048         8467166   4.0 GiB     0700  Linux/Windows =
data
/dev/sdc
   1            2048        17916206   8.5 GiB     0700  Linux/Windows =
data
#------------------------------------------------------------
# 2 GByte kopiert

# btrfs filesystem show
Label: 'SCSI'  uuid: 4d834705-5a65-4d1f-a8a0-a5ea9348db50
	Total devices 2 FS bytes used 2.10GB
	devid    1 size 4.04GB used 433.31MB path /dev/sda1
	devid    2 size 8.54GB used 2.25GB path /dev/sdc1

Btrfs Btrfs v0.19

# btrfs filesystem df /mnt/btr
Data: total=3D2.41GB, used=3D2.10GB
System: total=3D4.00MB, used=3D4.00KB
Metadata: total=3D264.00MB, used=3D2.79MB

# df -t btrfs
=46ilesystem    Type   1K-blocks      Used Available Use% Mounted on
/dev/sda1    btrfs    13189632   2202740  10714232  18% /mnt/btr

# gdisk -l
/dev/sda
   1            2048         8467166   4.0 GiB     0700  Linux/Windows =
data
/dev/sdc
   1            2048        17916206   8.5 GiB     0700  Linux/Windows =
data
#------------------------------------------------------------
# 7 GByte kopiert

# btrfs filesystem show
Label: 'SCSI'  uuid: 4d834705-5a65-4d1f-a8a0-a5ea9348db50
	Total devices 2 FS bytes used 9.03GB
	devid    1 size 4.04GB used 1.42GB path /dev/sda1
	devid    2 size 8.54GB used 8.25GB path /dev/sdc1

Btrfs Btrfs v0.19

# btrfs filesystem df /mnt/btr
Data: total=3D9.41GB, used=3D9.02GB
System: total=3D4.00MB, used=3D4.00KB
Metadata: total=3D264.00MB, used=3D11.80MB

# df -t btrfs
=46ilesystem    Type   1K-blocks      Used Available Use% Mounted on
/dev/sda1    btrfs    13189632   9467164   3459032  74% /mnt/btr

# gdisk -l
/dev/sda
   1            2048         8467166   4.0 GiB     0700  Linux/Windows =
data
/dev/sdc
   1            2048        17916206   8.5 GiB     0700  Linux/Windows =
data
#------------------------------------------------------------
# btrfs device add /dev/sdb1 /mnt/btr

# btrfs filesystem show
Label: 'SCSI'  uuid: 4d834705-5a65-4d1f-a8a0-a5ea9348db50
	Total devices 3 FS bytes used 9.12GB
	devid    3 size 136.73GB used 0.00 path /dev/sdb1
	devid    1 size 4.04GB used 1.42GB path /dev/sda1
	devid    2 size 8.54GB used 8.25GB path /dev/sdc1

Btrfs Btrfs v0.19

# btrfs filesystem df /mnt/btr
Data: total=3D9.41GB, used=3D9.10GB
System: total=3D4.00MB, used=3D4.00KB
Metadata: total=3D264.00MB, used=3D11.91MB

# df -t btrfs
=46ilesystem    Type   1K-blocks      Used Available Use% Mounted on
/dev/sda1    btrfs   156562592   9559000 146739216   7% /mnt/btr

# gdisk -l
/dev/sda
   1            2048         8467166   4.0 GiB     0700  Linux/Windows =
data
/dev/sdc
   1            2048        17916206   8.5 GiB     0700  Linux/Windows =
data
/dev/sdb
   1            2048       286747966   136.7 GiB   0700  Linux/Windows =
data
#------------------------------------------------------------
# btrfs filesystem balance /mnt/btr

# btrfs filesystem show
Label: 'SCSI'  uuid: 4d834705-5a65-4d1f-a8a0-a5ea9348db50
	Total devices 3 FS bytes used 9.11GB
	devid    3 size 136.73GB used 10.61GB path /dev/sdb1
	devid    1 size 4.04GB used 3.70GB path /dev/sda1
	devid    2 size 8.54GB used 8.08GB path /dev/sdc1

Btrfs Btrfs v0.19

# btrfs filesystem df /mnt/btr
Data, RAID0: total=3D21.89GB, used=3D9.10GB
System: total=3D4.00MB, used=3D4.00KB
Metadata, RAID0: total=3D511.88MB, used=3D10.15MB

# df -t btrfs
=46ilesystem    Type   1K-blocks      Used Available Use% Mounted on
/dev/sda1    btrfs   156562592   9557196  14370128  40% /mnt/btr

# gdisk -l
/dev/sda
   1            2048         8467166   4.0 GiB     0700  Linux/Windows =
data
/dev/sdc
   1            2048        17916206   8.5 GiB     0700  Linux/Windows =
data
/dev/sdb
   1            2048       286747966   136.7 GiB   0700  Linux/Windows =
data
#------------------------------------------------------------
# 8 GByte kopiert

# btrfs filesystem show
Label: 'SCSI'  uuid: 4d834705-5a65-4d1f-a8a0-a5ea9348db50
	Total devices 3 FS bytes used 17.02GB
	devid    3 size 136.73GB used 10.61GB path /dev/sdb1
	devid    1 size 4.04GB used 3.70GB path /dev/sda1
	devid    2 size 8.54GB used 8.08GB path /dev/sdc1

Btrfs Btrfs v0.19

# btrfs filesystem df /mnt/btr
Data, RAID0: total=3D21.89GB, used=3D17.00GB
System: total=3D4.00MB, used=3D4.00KB
Metadata, RAID0: total=3D511.88MB, used=3D18.66MB

# df -t btrfs
=46ilesystem    Type   1K-blocks      Used Available Use% Mounted on
/dev/sda1    btrfs   156562592  17850436   6085608  75% /mnt/btr

# gdisk -l
/dev/sda
   1            2048         8467166   4.0 GiB     0700  Linux/Windows =
data
/dev/sdc
   1            2048        17916206   8.5 GiB     0700  Linux/Windows =
data
/dev/sdb
   1            2048       286747966   136.7 GiB   0700  Linux/Windows =
data
#------------------------------------------------------------
# btrfs filesystem balance /mnt/btr

# btrfs filesystem show
Label: 'SCSI'  uuid: 4d834705-5a65-4d1f-a8a0-a5ea9348db50
	Total devices 3 FS bytes used 17.08GB
	devid    3 size 136.73GB used 9.08GB path /dev/sdb1
	devid    1 size 4.04GB used 2.09GB path /dev/sda1
	devid    2 size 8.54GB used 8.08GB path /dev/sdc1

Btrfs Btrfs v0.19

# btrfs filesystem df /mnt/btr
Data, RAID0: total=3D19.00GB, used=3D17.06GB
System: total=3D4.00MB, used=3D4.00KB
Metadata, RAID0: total=3D255.94MB, used=3D18.51MB

# df -t btrfs
=46ilesystem    Type   1K-blocks      Used Available Use% Mounted on
/dev/sda1    btrfs   156562592  17911352   6118356  75% /mnt/btr

# gdisk -l
/dev/sda
   1            2048         8467166   4.0 GiB     0700  Linux/Windows =
data
/dev/sdc
   1            2048        17916206   8.5 GiB     0700  Linux/Windows =
data
/dev/sdb
   1            2048       286747966   136.7 GiB   0700  Linux/Windows =
data
#------------------------------------------------------------



and then follows the problem I've told last year: "no space left on =20
device ...". In this special case: even not enough place for deleting =20
one partition.

Trying "btrfs device delete ..." without previous "balance" leads to

# btrfs device delete /dev/sdc1 /mnt/btr
# endet mit "error removing the device '/dev/sdc1'"


Viele Gruesse!
Helmut
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^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: How to remove a device on a RAID-1 before replacing it?
  2011-03-29 20:21 ` cwillu
  2011-03-29 20:45   ` Helmut Hullen
@ 2011-03-29 21:01   ` Andrew Lutomirski
  2011-03-29 21:15     ` Hugo Mills
  1 sibling, 1 reply; 5+ messages in thread
From: Andrew Lutomirski @ 2011-03-29 21:01 UTC (permalink / raw)
  To: cwillu; +Cc: linux-btrfs

On Tue, Mar 29, 2011 at 4:21 PM, cwillu <cwillu@cwillu.com> wrote:
> On Tue, Mar 29, 2011 at 2:09 PM, Andrew Lutomirski <luto@mit.edu> wro=
te:
>> I have a disk with a SMART failure. =A0It still works but I assume i=
t'll
>> fail sooner or later.
>>
>> I want to remove it from my btrfs volume, replace it, and add the ne=
w
>> one. =A0But the obvious command doesn't work:
>>
>> # btrfs device delete /dev/dm-5 /mnt/foo
>> ERROR: error removing the device '/dev/dm-5'
>>
>> dmesg says:
>> btrfs: unable to go below two devices on raid1
>>
>> With mdadm, I would fail the device, remove it, run degraded until I
>> get a new device, and hot-add that device.
>>
>> With btrfs, I'd like some confirmation from the fs that data is
>> balanced appropriately so I won't get data loss if I just yank the
>> drive. =A0And I don't even know how to tell btrfs to release the dri=
ve
>> so I can safely remove it.
>>
>> (Mounting with -o degraded doesn't help. =A0I could umount, remove t=
he
>> disk, then remount, but that feels like a hack.)
>
> There's no "nice" way to remove a failing disk in btrfs right now
> ("btrfs dev delete" is more of a online management thing to politely
> remove a perfectly functional disk you'd like to use for something
> else.) =A0As I understand things, the only way to do it right now is =
the
> umount, remove disk, remount w/ degraded, and then btrfs add the new
> device.
>

Well, the disk *is* perfectly functional.  It just won't be for long.

I guess what I'm saying is that either btrfs dev delete isn't really
working -- I want to be able to convert to non-RAID and back or
degraged and back or something else equivalent.

--Andy
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^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: How to remove a device on a RAID-1 before replacing it?
  2011-03-29 21:01   ` Andrew Lutomirski
@ 2011-03-29 21:15     ` Hugo Mills
  0 siblings, 0 replies; 5+ messages in thread
From: Hugo Mills @ 2011-03-29 21:15 UTC (permalink / raw)
  To: Andrew Lutomirski; +Cc: cwillu, linux-btrfs

[-- Attachment #1: Type: text/plain, Size: 2752 bytes --]

On Tue, Mar 29, 2011 at 05:01:39PM -0400, Andrew Lutomirski wrote:
> On Tue, Mar 29, 2011 at 4:21 PM, cwillu <cwillu@cwillu.com> wrote:
> > On Tue, Mar 29, 2011 at 2:09 PM, Andrew Lutomirski <luto@mit.edu> wrote:
> >> I have a disk with a SMART failure.  It still works but I assume it'll
> >> fail sooner or later.
> >>
> >> I want to remove it from my btrfs volume, replace it, and add the new
> >> one.  But the obvious command doesn't work:
> >>
> >> # btrfs device delete /dev/dm-5 /mnt/foo
> >> ERROR: error removing the device '/dev/dm-5'
> >>
> >> dmesg says:
> >> btrfs: unable to go below two devices on raid1
> >>
> >> With mdadm, I would fail the device, remove it, run degraded until I
> >> get a new device, and hot-add that device.
> >>
> >> With btrfs, I'd like some confirmation from the fs that data is
> >> balanced appropriately so I won't get data loss if I just yank the
> >> drive.  And I don't even know how to tell btrfs to release the drive
> >> so I can safely remove it.
> >>
> >> (Mounting with -o degraded doesn't help.  I could umount, remove the
> >> disk, then remount, but that feels like a hack.)
> >
> > There's no "nice" way to remove a failing disk in btrfs right now
> > ("btrfs dev delete" is more of a online management thing to politely
> > remove a perfectly functional disk you'd like to use for something
> > else.)  As I understand things, the only way to do it right now is the
> > umount, remove disk, remount w/ degraded, and then btrfs add the new
> > device.
> >
> 
> Well, the disk *is* perfectly functional.  It just won't be for long.
> 
> I guess what I'm saying is that either btrfs dev delete isn't really
> working -- I want to be able to convert to non-RAID and back or
> degraged and back or something else equivalent.

   RAID conversion isn't quite ready yet, sadly. As I understand it,
you've got two options:

 - Yoink the drive (thus making the fs run in degraded mode), add the
   new one, and balance to spread the duplicate data onto the new
   volume.

 - Add the new drive to the FS first, then use btrfs dev del to remove
   the original device. This should end up writing all the replicated
   data to the new drive as it "removes" the data from the old one.

   Of the two options, the latter is (for me) the favourite, as you
don't end up with a filesystem that's running on just a single copy of
the data.

   Hugo.

-- 
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
  PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk
  --- Prof Brain had been in search of The Truth for 25 years, with ---  
             the intention of putting it under house arrest.             

[-- Attachment #2: Digital signature --]
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^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2011-03-29 21:15 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2011-03-29 20:09 How to remove a device on a RAID-1 before replacing it? Andrew Lutomirski
2011-03-29 20:21 ` cwillu
2011-03-29 20:45   ` Helmut Hullen
2011-03-29 21:01   ` Andrew Lutomirski
2011-03-29 21:15     ` Hugo Mills

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