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Operating Systems Linux Red Hat Physical Volume Create Conundrum Post 302852463 by scotbuff on Wednesday 11th of September 2013 03:34:18 PM
Old 09-11-2013
Physical Volume Create Conundrum

I want to start by saying I already resolved my issue but I want to understand why I am seeing what I am seeing.

I have a server with a RAID controller two 500GB drives and six 600GB drives. The two 500GB drives are mirrored and have the OS installed on them. The six 600GB they wanted set as RAID0 and wanted them in a new volume group. My issue was getting the full size out of the RAID0 Virtual Disk.

On boot I saw the disk:
sd 0:2:1:0: [sdb] 7025983488 512-byte logical blocks: (3.59 TB/3.27 TiB)

I work mostly with LUNs and generally I can just do a pvcreate and I am ready to use the disk. But I could not issue a pvcreate on /dev/sdb and it seemed to need to be partitioned. So I used fdisk using this procedure, which I found to be the same on Red Hat's website:
Create Linux Partition

Once I had a partition I was issuing a pvcreate /dev/sdb1 and each time I ended up with only 2TB of usable space.
Code:
[root@testserv dev]# pvcreate /dev/sdb1
  Physical volume "/dev/sdb1" successfully created
[root@testserv dev]# pvscan
  PV /dev/sda2   VG vg01            lvm2 [464.75 GiB / 355.75 GiB free]
  PV /dev/sdb1                      lvm2 [2.00 TiB]

I ended up just issuing a pvremove, removing the partition and issueing a vgcreate against the raw device. I noticed that the vgcreate created the physical volume for me and it was the correct size.
Code:
[root@testserv ~]# vgcreate scratchvg /dev/sdb
  No physical volume label read from /dev/sdb
  Physical volume "/dev/sdb" successfully created
  Volume group "scratchvg" successfully created
[root@testserv ~]# pvscan
  PV /dev/sdb    VG scratchvg   lvm2 [3.27 TiB / 3.27 TiB free]
  PV /dev/sda2   VG vg01        lvm2 [464.75 GiB / 355.75 GiB free]
  Total: 2 [3.73 TiB] / in use: 2 [3.73 TiB] / in no VG: 0 [0   ]

My question is, what am I missing? I am completely fine with just skipping the fdisk and pvcreate steps but I thought I had to do those steps. What was I doing wrong? What is the proper procedure when taking a Virtual Disk presented by a RAID controller and creating or adding it to a volume group? I guess my own answer would be the procedure that works, but since I found so many references to using fdisk and partitioning the disk I am curious why that was not working for me. Thanks.
 

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MLXCONTROL(8)						    BSD System Manager's Manual 					     MLXCONTROL(8)

NAME
mlxcontrol -- Mylex DAC-family RAID management utility SYNOPSIS
mlxcontrol <command> [args] mlxcontrol status [-qv] [drive] mlxcontrol rescan controller [controller ...] mlxcontrol detach drive [drive ...] mlxcontrol detach -a mlxcontrol check drive mlxcontrol config controller mlxcontrol help command DESCRIPTION
The mlxcontrol utility provides status monitoring and management functions for devices attached to the mlx(4) driver. Controller names are of the form "mlxN" where N is the unit number of the controller. Drive names are of the form "mlxdN" where N is the unit number of the drive. Do not specify the path to a device node. status Print the status of controllers and system drives. If one or more drives are specified, only print information about these drives, otherwise print information about all controllers and drives in the system. With the -v flag, display much more verbose informa- tion. With the -q flag, do not print any output. This command returns 0 if all drives tested are online, 1 if one or more drives are critical and 2 if one or more are offline. rescan Rescan one or more controllers for non-attached system drives (e.g. drives that have been detached or created subsequent to driver initialisation). If the -a flag is supplied, rescan all controllers in the system. detach Detach one or more system drives. Drives must be unmounted and not opened by any other utility for this command to succeed. If the -a flag is supplied, detach all system drives from the nominated controller. check Initiate a consistency check and repair pass on a redundant system drive (e.g. RAID1 or RAID5). The controller will scan the system drive and repair any inconsistencies. This command returns immediately; use the status command to monitor the progress of the check. rebuild Requires two arguments, controller and physdrive as specified in the output of the status command. All system drives using space on the physical drive physdrive are rebuilt, reconstructing all data on the drive. Note that each controller can only perform one rebuild at a time. This command returns immediately; use the status command to monitor the progress of the rebuild. config Print the current configuration from the nominated controller. This command will be updated to allow addition/deletion of system drives from a configuration in a future release. help Print usage information for command. AUTHORS
The mlxcontrol utility was written by Michael Smith <msmith@FreeBSD.org>. BUGS
The config command does not yet support modifying system drive configuration. Error log extraction is not yet supported. BSD
April 10, 2000 BSD
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