[DRBD-user] DRBD attempts to access beyond end of device

Nate Seif seifn at rstechnicalservices.com
Thu Feb 28 17:27:50 CET 2008

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



On Wed, 27 Feb 2008, Lars Ellenberg wrote:

> On Wed, Feb 27, 2008 at 01:07:04PM -0500, Nate Seif wrote:
>>
>>
>> On Wed, 27 Feb 2008, Lars Ellenberg wrote:
>>
>>> On Tue, Feb 26, 2008 at 04:14:36PM -0500, Nate Seif wrote:
>>>> Hello all:
>>>> I intermittently experience the errors below while running DRBD and would
>>>> like to correct whatever condition is causing DRBD to randomly lose pages.
>>>> My hard disks and partitions are identical and have never given me
>>>> problems previously. I don't see any other disk I/O errors in my logs. And
>>>> it appears that occassionally (not always) these errors are preceded by a
>>>> resync of the two disks.
>>>>
>>>> Why would DRBD "attempt to access beyond end of device"?
>>>>
>>>> I am running DRBD 8.06 on Gentoo Linux as I could not get my latest
>>>> Gentoo kernel to load the DRBD module where version > 8.06. Metadata is
>>>> "internal" and I'm running Protocol C. I'd be happy to post my drbd.conf
>>>> page if necessary.
>>>>
>>>>
>>>> Feb 26 08:21:46 <hostname> attempt to access beyond end of device
>>>> Feb 26 08:21:46 <hostname> drbd0: rw=1, want=211992584, limit=211986944
>>>> Feb 26 08:21:46 <hostname> Buffer I/O error on device drbd0, logical block
>>>> 26499072
>>>> Feb 26 08:21:46 <hostname> lost page write due to I/O error on drbd0
>>>> Feb 26 08:21:46 <hostname> attempt to access beyond end of device
>>>> Feb 26 08:21:46 <hostname> drbd0: rw=1, want=211992592, limit=211986944
>>>> Feb 26 08:21:46 <hostname> Buffer I/O error on device drbd0, logical block
>>>> 26499073
>>>> Feb 26 08:21:46 <hostname> lost page write due to I/O error on drbd0
>>>>
>>>>
>>>> Any ideas, tips, help, etc. is much appreciated. Thank you -
>>>
>>> let me guess:
>>> you did mkfs /dev/sda1, not mkfs /dev/drbd0?
>>> well, you screwed up.
>>
>> I did NOT mkfs on /dev/hda4. (I have DRBD running on a pair of IDE/PATA
>> disks and no SATA drives in either system.)
>>
>> I partitioned my disks with fdisk. I have identical drives with
>> identically sized partitions. I compiled the DRBD module, started DRBD,
>> mounted /dev/drbd0 (not /dev/hda4), and formatted drbd0 with an ext3
>> file system on the primary only after I got DRBD up and running months
>> ago.
>
> please do
>
>      tune2fs -l /dev/mapper/vg00--bk1-root |
> 	grep -e ^Block.count: -e ^Block.size:
>
> you get two numbers.
> multiply those, you get the size (in bytes)
> your ext3 thinks it is occupying.
> which is the size of the partition you run the mkfs on, at the time of
> the mkfs run, unless you used special options.
>
> now, do
> 	grep -e hda4 -e drbd0 /proc/partitions
>
> you again get two numbers, this time unit is kilo byte.
> that is the size of the partitions as the kernel sees them now.
> according to the logs above (the limit= is unit sectors),
> drbd0 will be 105993472 kB.
> I dare say hda4 will be somewhat larger, my best guess, given the
> information I have, is that hda4 will be 105996740 kB.
> and that this also matches what the tune2fs reports.
>
>> My logs did not start recording these errors until several weeks ago.
>
> which probably only means that the file system slowly filled up,
> and now starts actually _using_ those areas which are no longer there,
> because they are now occupied by the drbd meta data.

I have used very little (only 7%) of the space on /dev/drbd0. 
<hostname> ~ # df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/hda3              12G  6.2G  4.6G  58% /
udev                   10M  176K  9.9M   2% /dev
shm                   997M     0  997M   0% /dev/shm
/dev/drbd0            100G  5.8G   89G   7% /rs2

<hostname> ~ # df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/hda3             11812248   6443008   4769204  58% /
udev                     10240       176     10064   2% /dev
shm                    1020808         0   1020808   0% /dev/shm
/dev/drbd0           104332960   6037048  92996076   7% /rs2


Does DRBD shrink the file system on /dev/drbd0 periodically to accomodate 
its meta data? If so, is the kernel made aware of this? I seem to remember 
reading somewhere, though, that internal metadata was a fixed 128 MB at 
the end of the device. In my case, internal metadata should occupy 128 MB 
at end of /dev/hda4 and  /dev/drbd0 should be correspondingly 128 MB 
smaller than /dev/hda4, correct?

Thank you for your time, Lars -


Nate






>
> -- 
> : Lars Ellenberg                           http://www.linbit.com :
> : DRBD/HA support and consulting             sales at linbit.com :
> : LINBIT Information Technologies GmbH      Tel +43-1-8178292-0  :
> : Vivenotgasse 48, A-1120 Vienna/Europe     Fax +43-1-8178292-82 :
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