[linux-lvm] LVM questions & problems.

[Heinz J. Mauelshagen]

On Sun, May 06, 2001 at 09:05:13PM -0400, Rupert Heesom wrote:
> I'm practicing doing some LVM commands, and am coming up with some
> problems -
> 
> Most disconcerting is that when I try to create a directory in the LV, I
> get the following error - (this does not happen all the time, but almost
> all the time 99%) -
> 
> [root at localhost Tmp]# mkdir test1
> mkdir: cannot create directory `test1': Input/output error

You didn't metion, if the filesystem is still in a sane state.

Did you check your syslog for "accessess beyond the end of the device"
which indicate fs related problems?

If so: did you run fsck to fix those and did you retest?

> 
> Creating normal files on the LV is not a problem.
> 
> Also, the figures in the following outputs don't seem to make sense to
> me -
> 
> 287Mb of space taken on my LV lvol1 (shown using du -h).

du is a filesystem tool which tells you how much space is used
from the fs perspective.
The LV tools provide information from the underlying block device being
exposed by the LVM to the filesytem or other users (like databases etc.).

> 
> LV lvol1 - shows all 75 logical extends taken, I'm assuming filling up
> the 300Mb LV size.
> 
> LV Size                300 MB
> Current LE             75
> Allocated LE           75

O.k.
That shows, that you have a 300M logical volume, which you said above.

vgdisplay on your volume group gives you (beside other information)
the size of the physical extents (PEs) which is 4M by default.

You can change that in order to address bigger configurations with
"vgcreate -s". Please see "man vgcreate" for further details.

> 
> 
> PV shows too many physical extends used for the proportion of disk space
> used. -
> 
> Total PE              76
> Free PE               1

That's ok because you allocated 75PEs which are 300M based on
4M PE size.

> 
> PVdisplay shows too many physical extents used again
> 
> Total PE              76
> Free PE               1
> Allocated PE          75

Same as above.


Please have a look at the LVM howto at www.sistina.com/lvm
for further hints on LVM usage.


Regards,
Heinz    -- The LVM Guy --


> 
> 
> ----------------------------------------
> 
> LVM command outputs
> -------------------
> 
> [root at localhost Tmp]# lvdisplay /dev/vg/lvol1
> lvdisplay
> --- Logical volume ---
> LV Name                /dev/vg/lvol1
> VG Name                vg
> LV Write Access        read/write
> LV Status              available
> LV #                   1
> # open                 1
> LV Size                300 MB
> Current LE             75
> Allocated LE           75
> Allocation             next free
> Read ahead sectors     120
> Block device           58:0
> 
> 
> [root at localhost Tmp]# pvdisplay /dev/sdb1
> pvdisplay
> --- Physical volume ---
> PV Name               /dev/sdb1
> VG Name               vg
> PV Size               305.89 MB / NOT usable 1.89 MB [LVM: 121 KB]
> PV#                   1
> PV Status             available
> Allocatable           yes
> Cur LV                1
> PE Size (KByte)       4096
> Total PE              76
> Free PE               1
> Allocated PE          75
> PV UUID               wm3nGp-pEem-0byC-3JOs-OFs4-3kv2-EkPxaK
> 
> 
> [root at localhost Tmp]# vgdisplay
> vgdisplay
> --- Volume group ---
> VG Name               vg
> VG Access             read/write
> VG Status             available/resizable
> VG #                  0
> MAX LV                256
> Cur LV                1
> Open LV               1
> MAX LV Size           255.99 GB
> Max PV                256
> Cur PV                1
> Act PV                1
> VG Size               304 MB
> PE Size               4 MB
> Total PE              76
> Alloc PE / Size       75 / 300 MB
> Free  PE / Size       1 / 4 MB
> VG UUID               0ZyZNT-53L9-tAFJ-GCa4-1Zr5-nZli-IFIbIP
> 
> 
> -- 
> regs
> rupert
> 
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> linux-lvm at sistina.com
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Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen at Sistina.com                           +49 2626 141200
                                                       FAX 924446
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