[Bug 320638] Re: hot-add/remove in mixed (IDE/SATA/USB/SD-card/...) RAIDs with device mapper on top => data corruption (bio too big device md0 (248 > 240))

Sat Mar 2 21:52:27 UTC 2013

I'm using SATA drives for LVM on RAID 1. RAID is configured with
internal bitmap, so resyncing is quite fast.

In order to do the best kind of backup, I replace my drives to keep backups of complete systems.
There is a very good reason for this, since in the case of a complete desaster I simply take the last backup disk and use it in a working hardware.

So, sometimes it would be quite useful, to also use some USB external storage to connect a hard drive.
But, because of this error, the whole procedure is not possible.

I know it works with eSATA,
but this error claims always with USB connected drives.

Using rsync is not as simple as using a hotplug script that initiates
raid resync.

I don't know, how it behaves with USB3.

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Title:
  hot-add/remove in mixed (IDE/SATA/USB/SD-card/...)  RAIDs with device
  mapper on top => data corruption (bio too big device md0 (248 > 240))

Status in The Linux Kernel:
  Confirmed
Status in mdadm - Tool for managing linux software RAID arrays.:
  Confirmed
Status in “debian-installer” package in Ubuntu:
  Invalid
Status in “linux” package in Ubuntu:
  Won't Fix
Status in “mdadm” package in Ubuntu:
  Confirmed
Status in “ubiquity” package in Ubuntu:
  Invalid

Bug description:
  Problem: md changes max_sector setting of an already running and busy
  md device, when a (hotplugable) device is added or removed. However,
  the device mapper and filesystem layer on top of the raid can not
  (always?) cope with that.

  Observations:
  * "bio too big device mdX (248 > 240)" messages in the syslog
  * read/write errors (some dropped silently, no noticable errors reported during operation, until things like dhcpclient looses its IP etc.)

  Expected:
  Adding and removing members to running raids (hotplugging) should not change the raid device characteristics. If the new member supports only smaller max_sector values, buffer and split the data steam, until the raid device can be set up from a clean state with a more appropriate max_sector value. To avoid buffering and splitting in the future, md could save the smallest max_sector value of the known members in the superblock, and use that when setting up the raid even if that member is not present.

  Note: This is reproducible in much more common scenarios as the original reporter had (e.g. --add a USB (3.0 these days) drive to an already running SATA raid1 and grow the number of devices).
  ---

  This is on a MSI Wind U100 and I've got the following stack running:
  HDD & SD card (USB card reader) -> RAID1 -> LUKS -> LVM -> Reiser

  Whenever I remove the HDD from the Raid1
  > mdadm /dev/md0 --fail /dev/sda2
  > mdadm /dev/md0 --remove /dev/sda2)
  for powersaving reasons, I cannot run any apt related tools.

  > sudo apt-get update
  [...]
  Hit http://de.archive.ubuntu.com intrepid-updates/multiverse Sources
  Reading package lists... Error!
  E: Read error - read (5 Input/output error)
  E: The package lists or status file could not be parsed or opened.

  Taking a look at the kernel log shows (and many more above):
  > dmesg|tail
  [ 9479.330550] bio too big device md0 (248 > 240)
  [ 9479.331375] bio too big device md0 (248 > 240)
  [ 9479.332182] bio too big device md0 (248 > 240)
  [ 9611.980294] bio too big device md0 (248 > 240)
  [ 9742.929761] bio too big device md0 (248 > 240)
  [ 9852.932001] bio too big device md0 (248 > 240)
  [ 9852.935395] bio too big device md0 (248 > 240)
  [ 9852.938064] bio too big device md0 (248 > 240)
  [ 9853.081046] bio too big device md0 (248 > 240)
  [ 9853.081688] bio too big device md0 (248 > 240)

  $ sudo mdadm --detail /dev/md0
  /dev/md0:
          Version : 00.90
    Creation Time : Tue Jan 13 11:25:57 2009
       Raid Level : raid1
       Array Size : 3871552 (3.69 GiB 3.96 GB)
    Used Dev Size : 3871552 (3.69 GiB 3.96 GB)
     Raid Devices : 2
    Total Devices : 1
  Preferred Minor : 0
      Persistence : Superblock is persistent

    Intent Bitmap : Internal

      Update Time : Fri Jan 23 21:47:35 2009
            State : active, degraded
   Active Devices : 1
  Working Devices : 1
   Failed Devices : 0
    Spare Devices : 0

             UUID : 89863068:bc52a0c0:44a5346e:9d69deca (local to host m-twain)
           Events : 0.8767

      Number   Major   Minor   RaidDevice State
         0       0        0        0      removed
         1       8       17        1      active sync writemostly   /dev/sdb1

  $ sudo ubuntu-bug -p linux-meta
  dpkg-query: failed in buffer_read(fd): copy info file `/var/lib/dpkg/status': Input/output error
  dpkg-query: failed in buffer_read(fd): copy info file `/var/lib/dpkg/status': Input/output error
  [...]

  Will provide separate attachements.

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