[Bug 478794] [NEW] grub-probe does a linear scan on large drives

[Tim Hatch]

Public bug reported:

Binary package hint: grub2

I have a 3ware 9650se with 4x 1.5TB drives RAID 5.  This exposes an
array of approx 4TiB to Linux as /dev/sdd and it takes a VERY long time
during the installer (a fresh install) and upon an update of grub-pc
today, to create the grub config by probing.

/dev/sdd is configured as an lvm pv, which contains a single lv, which
contains a GPT with a single partition of the whole size formatted ext3.

Expected:

If grub is supposed to probe for other OSes, that such probes complete
within a matter of seconds or provide progress reports.  I don't expect
it to scan entire drives, especially drives so large.

Actual:

It scans the entire lvm-gpt-ext3 drive 4KiB at a time, with no progress,
in both the installer and when running dpkg-reconfigure.  I just timed
it and this took 21m33s to complete.

Notes:

The bug as I see it is that it's doing a linear scan at all, out of the
box.  There's obviously only one partition involved here, and it didn't
at least inform me before the bootloader progress bar hung at 50% during
the 9.10 installer.  An strace log is attached.  This scan launches
several instances of grub-probe, and the whole process takes about half
an hour.

Release: 9.10 using alternate installer cd
grub-pc version: 1.97~beta4-1ubuntu4 (but occurred with an earlier one as well)

Let me know what other information would be helpful.

ProblemType: Bug
Architecture: amd64
Date: Sun Nov  8 14:17:59 2009
DistroRelease: Ubuntu 9.10
NonfreeKernelModules: nvidia
Package: grub-pc 1.97~beta4-1ubuntu4
ProcEnviron:
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-14.48-generic
SourcePackage: grub2
Uname: Linux 2.6.31-14-generic x86_64

** Affects: grub2 (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug

-- 
grub-probe does a linear scan on large drives
https://bugs.launchpad.net/bugs/478794
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