[linux-lvm] pvcreate can't use entire disk?
f-lvm at media.mit.edu
f-lvm at media.mit.edu
Mon Jan 23 23:02:39 UTC 2006
Date: Mon, 23 Jan 2006 22:35:16 +0000
From: Alasdair G Kergon <agk at redhat.com>
On Mon, Jan 23, 2006 at 05:26:00PM -0500, f-lvm at media.mit.edu wrote:
> "Device /dev/hdd not found." The disk is surely online: I can
> I would have -expected- pvcreate to complain about a partition table
> existing
The currrent internal structure of LVM2 makes that difficult.
Add -vvvv to commands for more information like that.
Invalid devices are filtered out at a low level in the libraries
so tools such as 'pvcreate' never see them.
If your disk has a partition table, then LVM2 insists you use those
partitions to reduce the risk of accidents.
Ah. That's directly contrary to the LVM2 howto at
http://www.tldp.org/HOWTO/LVM-HOWTO/initdisks.html,
which says, "If you get an error that LVM can't initialize
a disk with a partition table on it, ..." etc.
The manpage also doesn't claim that not erasing an existing partition
table will cause pvcreate to simply fail as if the hardware is
offline---pvcreate should warn! (And, as if obvious from -vvvv (which
is -also- undocumented! Only -v and --verbose are documented, but not
their repetition to get more info), pvcreate knew damned well what was
going on---but didn't tell -me-. Well, okay, maybe some library
beneath pvcreate knew and didn't tell pvcreate, but in that case,
we certainly had incomplete and/or misleading documentation in two
places.)
Is this a problem with pvcreate in its original instantiation, or with
a Debian version, or with Ubuntu? I'm planning on bugreporting this
to Ubuntu anyway, but it'd be nice if it made its way upstream as
expeditiously as possible. (And I'm CC'ing the HOWTO author
directly.)
[And why was I in this situation? Because I'm -very- cautious about
things that might wipe entire disks, and I wanted to verify that
pvcreate failed as documented before giving it the go-ahead.
Apparently, though, the documentation mislead me...]
Anyway, thanks!
> (at which point I would have zeroed it and tried again)
Did you try that?
(And then you might need to run 'vgscan'.)
Yes, I tried zeroing the first 1k, and -now- pvcreate apparently works
fine. vgscan only returned my original VG, but that makes sense,
since I haven't tried to actually instantiate a VG on the new disk
yet. Transcripts of failing and working case below:
~# pvcreate /dev/hdd
Device /dev/hdd not found.
~# strings /dev/hdd | head -1
LILO
~# dd if=/dev/hdd bs=512 count=1
[ . . . random garbage deleted so it won't gronk your mailreader . . . ]
1+0 records in
1+0 records out
512 bytes transferred in 0.000133 seconds (3846551 bytes/sec)
~# pvcreate --version
LVM version: 2.01.04 (2005-02-09)
Library version: 1.01.03 (2005-06-13)
Driver version: 4.4.0
~# pvcreate -vvvv /dev/hdd
#lvmcmdline.c:835 Processing: pvcreate -vvvv /dev/hdd
#lvmcmdline.c:838 O_DIRECT will be used
#config/config.c:773 Setting global/locking_type to 1
#config/config.c:758 Setting global/locking_dir to /var/lock/lvm
#locking/locking.c:137 File-based locking enabled.
#locking/file_locking.c:162 Locking /var/lock/lvm/P_orphans WB
#device/dev-cache.c:206 /dev/hdd: Added to device cache
#device/dev-io.c:376 Opened /dev/hdd RO
#device/dev-io.c:250 /dev/hdd: size is 390721968 sectors
#device/dev-io.c:308 WARNING: /dev/hdd already opened read-only
#device/dev-io.c:407 Closed /dev/hdd
#device/dev-io.c:376 Opened /dev/hdd RW
#device/dev-io.c:134 /dev/hdd: block size is 4096 bytes
#filters/filter.c:109 /dev/hdd: Skipping: Partition table signature found
#metadata/metadata.c:834 <backtrace>
#filters/filter-persistent.c:216 /dev/hdd: Skipping (cached)
#pvcreate.c:81 Device /dev/hdd not found.
#locking/file_locking.c:59 Unlocking /var/lock/lvm/P_orphans
#device/dev-io.c:407 Closed /dev/hdd
~# dd if=/dev/hdd of=hdd.1k bs=1k count=1
1+0 records in
1+0 records out
1024 bytes transferred in 0.004259 seconds (240427 bytes/sec)
~# dd if=/dev/zero of=/dev/hdd bs=1k count=1
1+0 records in
1+0 records out
1024 bytes transferred in 0.000137 seconds (7478965 bytes/sec)
~# blockdev --rereadpt /dev/hdd
~# pvcreate -vvvv /dev/hdd
#lvmcmdline.c:835 Processing: pvcreate -vvvv /dev/hdd
#lvmcmdline.c:838 O_DIRECT will be used
#config/config.c:773 Setting global/locking_type to 1
#config/config.c:758 Setting global/locking_dir to /var/lock/lvm
#locking/locking.c:137 File-based locking enabled.
#locking/file_locking.c:162 Locking /var/lock/lvm/P_orphans WB
#device/dev-cache.c:206 /dev/hdd: Added to device cache
#device/dev-io.c:376 Opened /dev/hdd RO
#device/dev-io.c:250 /dev/hdd: size is 390721968 sectors
#device/dev-io.c:308 WARNING: /dev/hdd already opened read-only
#device/dev-io.c:407 Closed /dev/hdd
#device/dev-io.c:376 Opened /dev/hdd RW
#device/dev-io.c:134 /dev/hdd: block size is 4096 bytes
#filters/filter-composite.c:31 Using /dev/hdd
#label/label.c:186 /dev/hdd: No label detected
#label/label.c:278 <backtrace>
#device/dev-io.c:250 /dev/hdd: size is 390721968 sectors
#config/config.c:778 metadata/pvmetadatasize not found in config: defaulting to 255
#config/config.c:778 metadata/pvmetadatacopies not found in config: defaulting to 1
#device/dev-io.c:250 /dev/hdd: size is 390721968 sectors
#device/dev-io.c:535 Wiping /dev/hdd at sector 4 length 8 sectors
#pvcreate.c:207 Set up physical volume for "/dev/hdd" with 390721584 available sectors
#label/label.c:209 Scanning for labels to wipe from /dev/hdd
#pvcreate.c:216 Zeroing start of device /dev/hdd
#device/dev-io.c:535 Wiping /dev/hdd at sector 0 length 4 sectors
#pvcreate.c:227 Writing physical volume data to disk "/dev/hdd"
#format_text/format-text.c:1039 Creating metadata area on /dev/hdd at sector 4 size 380 sectors
#label/label.c:326 /dev/hdd: Writing label to sector 1
Physical volume "/dev/hdd" successfully created
#locking/file_locking.c:59 Unlocking /var/lock/lvm/P_orphans
#device/dev-io.c:407 Closed /dev/hdd
~#
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