[DRBD-user] Increasing a DRBD array

Gerald Brandt gbr at majentis.com
Fri Oct 21 22:48:12 CEST 2011

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Hi, 

DRBD is running directly on md0. /dev/drbd1 is then exported via iSCSI. 

The logs show: 
Oct 21 15:34:53 iscsi-filer-1 kernel: [ 7.332010] drbd: initialized. Version: 8.3.7 (api:88/proto:86-91) 
Oct 21 15:34:53 iscsi-filer-1 kernel: [ 7.332012] drbd: GIT-hash: ea9e28dbff98e331a62bcbcc63a6135808fe2917 build by root at filer-1, 2011-03-05 08:29:38 
Oct 21 15:34:53 iscsi-filer-1 kernel: [ 7.332014] drbd: registered as block device major 147 
Oct 21 15:34:53 iscsi-filer-1 kernel: [ 7.332015] drbd: minor_table @ 0xffff88021dbaf300 
Oct 21 15:34:53 iscsi-filer-1 kernel: [ 7.334144] block drbd1: Starting worker thread (from cqueue [1489]) 
Oct 21 15:34:53 iscsi-filer-1 kernel: [ 7.334177] block drbd1: ==> truncating very big lower level device to currently maximum possible 8587575296 sectors <== 
Oct 21 15:34:53 iscsi-filer-1 kernel: [ 7.334179] block drbd1: ==>> using internal or flexible meta data may help <<== 
Oct 21 15:34:53 iscsi-filer-1 kernel: [ 7.334188] block drbd1: disk( Diskless -> Attaching ) 
Oct 21 15:34:53 iscsi-filer-1 kernel: [ 7.353306] Loading iSCSI transport class v2.0-870. 
Oct 21 15:34:53 iscsi-filer-1 kernel: [ 7.360582] skge eth0: disabling interface 
Oct 21 15:34:53 iscsi-filer-1 iscsid: iSCSI logger with pid=1515 started! 
Oct 21 15:34:53 iscsi-filer-1 kernel: [ 7.381956] iscsi: registered transport (iser) 
Oct 21 15:34:53 iscsi-filer-1 init: ssh main process (1162) terminated with status 255 
Oct 21 15:34:53 iscsi-filer-1 postfix/master[1411]: reload -- version 2.7.0, configuration /etc/postfix 
Oct 21 15:34:54 iscsi-filer-1 kernel: [ 7.584678] block drbd1: Found 57 transactions (3507 active extents) in activity log. 
Oct 21 15:34:54 iscsi-filer-1 kernel: [ 7.584684] block drbd1: Method to ensure write ordering: barrier 
Oct 21 15:34:54 iscsi-filer-1 kernel: [ 7.584691] block drbd1: Backing device's merge_bvec_fn() = ffffffffa00c0100 
Oct 21 15:34:54 iscsi-filer-1 kernel: [ 7.584694] block drbd1: max_segment_size ( = BIO size ) = 4096 
Oct 21 15:34:54 iscsi-filer-1 kernel: [ 7.584698] block drbd1: Adjusting my ra_pages to backing device's (32 -> 96) 
Oct 21 15:34:54 iscsi-filer-1 kernel: [ 7.584704] block drbd1: drbd_bm_resize called with capacity == 8587575296 
Oct 21 15:34:54 iscsi-filer-1 kernel: [ 7.603470] block drbd1: resync bitmap: bits=1073446912 words=16772608 
Oct 21 15:34:54 iscsi-filer-1 kernel: [ 7.603474] block drbd1: size = 4095 GB (4293787648 KB) 

The lines in yellow bug me. I don't recall see them before. 

I had a 4 disk RAID-6 md0 (4x2TB = 4 TB RAID-6). I added a single drive (5x2TB = 6 TB array). 

Any ideas? 

Gerald 

----- Original Message -----

> From: "Andreas Kurz" <andreas at hastexo.com>
> To: drbd-user at lists.linbit.com
> Sent: Friday, October 21, 2011 2:55:06 PM
> Subject: Re: [DRBD-user] Increasing a DRBD array

> On 10/21/2011 09:30 PM, Gerald Brandt wrote:
> > Hi,
> >
> > I've successfully resize the lower level RAID-6 array, and grown
> > it. I'm now attempting to resize drbd, and nothing seems to
> > happen.
> >
> > /dev/md0 is definitely bigger.
> >
> > What should I see during a drbd resize?

> You should see a DRBD resync of the newly added space.

> What is the lower level device of your DRBD resource? The whole md0,
> a
> partition on md0, a lv on a vg on a pv on md0?

> ... so if the lower level device has been resized on both nodes, DRBD
> should definitely grow on a "drbdadm resize".

> Did I mention that on starting DRBD it is resized automatically if a
> bigger lower level device is detected? ... have a look at the kernel
> logs...

> Regards,
> Andreas

> --
> Need help with DRBD?
> http://www.hastexo.com/now

> >
> > Gerald
> >
> >
> > ----- Original Message -----
> >> From: "Gerald Brandt" <gbr at majentis.com>
> >> To: drbd-user at lists.linbit.com
> >> Sent: Tuesday, October 18, 2011 7:08:55 AM
> >> Subject: Re: [DRBD-user] Increasing a DRBD array
> >>
> >> Hi,
> >>
> >> Okay, this is my list of what to do, and in what order:
> >>
> >> 1. remove the primary from DRBD
> >> 2. add the physical disk to the primary
> >> 3. add the primary back to DRBD and allow resync.
> >> 4. remove the secondary from DRBD
> >> 5. add the physical disk to the secondary
> >> 6. add the secondary back to DRBD and allow resync.
> >> 7. fdisk and add the disk to the RAID array on primary and
> >> secondary
> >> 8. grow the RAID array on the primary and secondary (while mounted
> >> or
> >> not mounted?)
> >> 9. drbdadm resize on the primary (can this be done while drbd is
> >> in
> >> use?)
> >> 10. expand the file system on the primary only (via Citrix
> >> XenServer
> >> (iSCSI))
> >>
> >> That sounds about right. As long as I don't lose data. (yeah,
> >> backups. That's left up to my client, but becomes my problem if
> >> they failed.)
> >>
> >> Gerald
> >>
> >>
> >>
> >> ----- Original Message -----
> >>> From: "Florian Haas" <florian at hastexo.com>
> >>> To: drbd-user at lists.linbit.com
> >>> Sent: Tuesday, October 18, 2011 3:53:11 AM
> >>> Subject: Re: [DRBD-user] Increasing a DRBD array
> >>>
> >>> On 2011-10-17 22:19, Matt Graham wrote:
> >>>>>> Your DRBD uses the MD RAID as its backing device, doesn't it?
> >>>>>> That means you'll have add the drive and resize your RAID
> >>>>>> first,
> >>>>>> then
> >>>>>> you can resize your DRBD, and then expand the file system.
> >>>>> Definitely built on top of the RAID. I'm a bit confused by
> >>>>> your
> >>>>> answer though. Step 8 grows the RAID array, and I don't have a
> >>>>> step
> >>>>> to grow DRBD. Does that mean I'm missing something?
> >>>>
> >>>> 8. mdadm --grow /dev/md0 (other mdadm options)
> >>>> Do that on both machines.
> >>>> 8.1 (on secondary) drbdsetup /dev/drbd0 resize
> >>>> 8.2 (on primary) drbdsetup /dev/drbd0 resize
> >>>
> >>> There's a "resize" subcommand for drbdadm too; no need to use
> >>> drbdsetup.
> >>> And it needs to be done on one node only. Just do "drbdadm resize
> >>> <resourcename>" on the primary while the two nodes are connected,
> >>> and
> >>> you're good to go.
> >>>
> >>>> The softRAID is below the DRBD device. Once the softRAID is
> >>>> larger, the DRBD device needs to be informed of this fact.
> >>>> When making arrays/devices larger, you go bottom-up; you make
> >>>> the hardware changes first, then softRAID changes, then DRBD
> >>>> changes, then filesystem changes.
> >>>> 9. (on primary) resize2fs /dev/drbd0
> >>>
> >>> If it's ext3 and if it supports on-line resizing, of course. But
> >>> that
> >>> should be obvious.
> >>>
> >>> Cheers,
> >>> Florian
> >>>
> >>> --
> >>> Need help with DRBD?
> >>> http://www.hastexo.com/knowledge/drbd
> >>> _______________________________________________
> >>> drbd-user mailing list
> >>> drbd-user at lists.linbit.com
> >>> http://lists.linbit.com/mailman/listinfo/drbd-user
> >>>
> >> _______________________________________________
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> >>
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