[CentOS] Rescan harddisk size without rebooting

kadafax kadafax at gmail.com
Wed Nov 9 22:16:42 UTC 2005


(I found that the module used was qla6320, dont know if there is an 
issue with this but I thought that the qla2200 would be more appropriate 
since the host card is a qla200.)
let's go:
Bryan J. Smith wrote:

>kadafax <kadafax at gmail.com> wrote:
>  
>
>>Quite there: the new size is reflected...but the disks
>>(I've got two virtual disks from the SAN, who are seen like
>>scsi disk by the system) are now described as /dev/sdd and
>>/dev/sde (initialy /dev/sdb and sdc)
>>
> Aww crap.  Yeah, forgot to mention you might need to release
>the previous device assignments.
>
how to release device assignments? I didn't find any clue on google.

>  Kernel 2.6 (CentOS 4) is
>better at doing that automagically than kernel 2.4 (CentOS
>3).  I assume you're on CentOS 3?
>  
>
nope CentOS 4.2

>>(below output from a "fdisk -l", the disc which grew is
>>initialy sdb). 
>>And a "pvdisplay" do not see any new physical extents
>>available (perhaps I'm missing something on this, I'm
>>totally new from this and way long to be totally cool with
>>it)
>>    
>>
>Part of the problem might be because we probably should have
>taken the volume group, and its physical extents, off-line
>before doing the previous.  I should have thought this
>through more, sorry.
>
( come on :) )
Will this take off-line the physical extents along with the VG? :
---
[root at X ~]# vgchange -a n /dev/VG-B/LV-B
---

>  Although it probably won't be of any
>issue either.
>
>You could run "vgscan" as see what happens.
>  
>
after the 'vgchange -a n', 'rmmod & modprobe' then the 'vgchange -a y':
---
[root at X ~]#  vgscan
  Reading all physical volumes.  This may take a while...
  Found volume group "VG-C" using metadata type lvm2
  Found volume group "VG-B" using metadata type lvm2
  Found volume group "VolGroup00" using metadata type lvm2
---

>>Should I be worried about the "non-valid partition" table
>>message? 
>>    
>>
>Nope.  Next time you boot, it will self-correct.  LVM is
>self-contained, so the vgscan handles locating all volumes.
>
>>I can use the LV (mount and work with files), so I don't
>>know if it is a problem. Maybe the fact that there is no
>>partition table for fdisk is why I can't make it grow?
>>    
>>
>
>Hmmm, not sure.  Again, maybe a vgscan would correct things?
>
>  
>
>>I mean, maybe I should have create first one 
>>partition (type LVM), then create a second one with the
>>extra size ?
>>Here is what I've done to create the logical volume:
>>---
>>[root at X ~]# pvcreate /dev/sdb
>>    
>>
>
>Well, that won't work because the volumes aren't there on
>/dev/sdb.
>
>  
>
>>[root at X ~]# vgcreate VG-B /dev/sdb
>>[root at X ~]# lvcreate -l 166911 VG-B -n LV-B
>>// Note: 166911 is the maximum number of physical extents
>>available 
>>before the grow
>>[root at X ~]# mkfs.ext3 /dev/VG-B/LV-B
>>---
>>from there I could use the volume.
>>    
>>
the above was what I initialy made to create the LV before adding a HD 
to the SAN, before trying to expand it without having to reboot.
More details:
In the SAN: 5 then 6 * 250GB HD in one disk pool (RAID 5)
                    2 Virtual disks: 1 * 250GB  <-- VG-C / LV-C
                                              3 * 250GB <-- I've 
initialy created the VG-B / LV-B with this capacity
                                                                       
then I added another 250GB HD to the pool and
                                                                       
assigned it to this virtual disk. Now I'm trying to
                                                                       
expand the VG/LV, without rebooting.
(raw available capacity is lesser than 250GB for each disk because in 
this SAN (AX100sc) the OS (winXP...) reserve 20GB on the first 3 HD and 
since the others are in the same pool, I've "lost" 20GB on each disk 
(OT: I found this a little crappy...))

>>---
>>[root at onyx install]# pvdisplay
>>  --- Physical volume ---
>>  PV Name               /dev/sde
>>  VG Name               VG-C
>>  PV Size               217.00 GB / not usable 0  
>>  Allocatable           yes (but full)
>>  PE Size (KByte)       4096
>>  Total PE              55551
>>  Free PE               0
>>  Allocated PE          55551
>>  PV UUID              
>>w3Q4hA-ALnz-4UuH-fdBB-FGOT-Rn2t-4iG2Vv
>>  
>>  --- Physical volume ---
>>  PV Name               /dev/sdd
>>  VG Name               VG-B
>>  PV Size               652.00 GB / not usable 0  
>>  Allocatable           yes (but full)
>>  PE Size (KByte)       4096
>>  Total PE              166911
>>  Free PE               0
>>  Allocated PE          166911
>>  PV UUID              
>>AFcoa6-6eJl-AAd3-G0Vt-OTXR-niPn-3bTLXu
>>  
>>  --- Physical volume ---
>>  PV Name               /dev/sda2
>>  VG Name               VolGroup00
>>  PV Size               136.50 GB / not usable 0  
>>  Allocatable           yes
>>  PE Size (KByte)       32768
>>  Total PE              4368
>>  Free PE               1
>>  Allocated PE          4367
>>  PV UUID              
>>OjQEXi-u3F8-wCXO-1eZY-W2j0-iZyG-5PwwnB
>>----
>>    
>>
>
>Well, you're volumes are clearly showing up on /dev/sdd and
>sde.  Those are probably the device(s) you have to target for
>expansion.
>  
>
but the /dev/sdb and sdc are gone, the PV have just followed the shift 
of the device assignments and the new available physical extents are not 
there. After putting off-line the VG (vgchange -a n) unloading then 
loading the qla module, the new correct size is shown by fdisk but not 
with LVM (no new physical extents appeared). How to gain the new extents 
within LVM when the HD growed up?

(It's late here in europe, I will be back tomorrow. Thanks again for 
support).


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