[Bug 1308423] [NEW] race between mdadm and scsi scan

[Nick Moffitt]

Public bug reported:

This brings back memories of the venerable old bug #75681

We're booting precise systems with the linux-image-generic-lts-saucy
kernel (3.11, as you'll see in the attached boot log), and have some
specialised SSD devices we RAID together to form a single block device.
Unfortunately, the md autodetection and assembly seems to happen before
all of these devices have reported in, causing a halted boot sitting at
a busybox prompt (not fun for servers!)

As a workaround, we set scsi_mod.scan=sync in the kernel boot options,
which makes boot block on the scsi scan.  I'm not sure that's the best
solution, but it felt the most appropriate at the time!

** Affects: mdadm (Ubuntu)
     Importance: Undecided
         Status: Confirmed

** Attachment added: "mdadm.txt"
   https://bugs.launchpad.net/bugs/1308423/+attachment/4085214/+files/mdadm.txt

** Description changed:

  This brings back memories of the venerable old bug #75681
  
  We're booting precise systems with the linux-image-generic-lts-saucy
  kernel (3.11, as you'll see in the attached boot log), and have some
  specialised SSD devices we RAID together to form a single block device.
  Unfortunately, the md autodetection and assembly seems to happen before
  all of these devices have reported in, causing a halted boot sitting at
  a busybox prompt (not fun for servers!)
  
- Essentially we need to set scsi_mod.scan=sync in the kernel boot
- options,
+ As a workaround, we set scsi_mod.scan=sync in the kernel boot options,
+ which makes boot block on the scsi scan.  I'm not sure that's the best
+ solution, but it felt the most appropriate at the time!

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https://bugs.launchpad.net/bugs/1308423

Title:
  race between mdadm and scsi scan

Status in “mdadm” package in Ubuntu:
  Confirmed

Bug description:
  This brings back memories of the venerable old bug #75681

  We're booting precise systems with the linux-image-generic-lts-saucy
  kernel (3.11, as you'll see in the attached boot log), and have some
  specialised SSD devices we RAID together to form a single block
  device.  Unfortunately, the md autodetection and assembly seems to
  happen before all of these devices have reported in, causing a halted
  boot sitting at a busybox prompt (not fun for servers!)

  As a workaround, we set scsi_mod.scan=sync in the kernel boot options,
  which makes boot block on the scsi scan.  I'm not sure that's the best
  solution, but it felt the most appropriate at the time!

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