[CentOS] can't create large LVM, even though pvscan shows enough space left

[Rudi Ahlers]

On Fri, Feb 25, 2011 at 4:34 PM, Robert Heller <heller at deepsoft.com> wrote:
> At Fri, 25 Feb 2011 15:15:34 +0200 CentOS mailing list <centos at centos.org> wrote:
>
>>
>> I'm trying to create a 500GB lv volume on a 500GB physical volume, but can't:
>>
>> [root at francois-pc ~]# pvscan
>>   PV /dev/sdd                  VG freenas      lvm2 [500.00 GB / 500.00 GB free]
>>   PV /dev/sdc                  VG thecus       lvm2 [1010.00 GB /
>> 910.00 GB free]
>>   PV /dev/mapper/ddf1_RAIDp2   VG VolGroup00   lvm2 [931.25 GB / 0    free]
>>   Total: 3 [2.38 TB] / in use: 3 [2.38 TB] / in no VG: 0 [0   ]
>> [root at francois-pc ~]# lvcreate -L 500gig -n 500G freenas
>>   Insufficient free extents (127999) in volume group freenas: 128000 required
>>
>> Even dropping the size a bit, I get this:
>>
>> [root at francois-pc ~]# lvcreate -L 500gig -n 450G freenas
>>   Insufficient free extents (127999) in volume group freenas: 128000 required
>
> '-n' is the *name*, -L is the size.  You are still asking for a 500G
> sized volume.


hehe, how did I miss that? Thanx for pointing it out to me. I thought
I changed the size, not the name.


>
> Try this:
>
> lvcreate -l 100%FREE -n volume freenas
>
> This will create a logical volume (named volume) that uses all of the
> *available* free space, which will be *slightly* less than the 500B of
> the VG.

Ok, this is kinda confusing.

How could I create a 500GB volume this way, but not with specifying
the actual size?


[root at francois-pc ~]# lvcreate -l 100%FREE -n 500-gig freenas
  Logical volume "500-gig" created

[root at francois-pc ~]# pvscan
  PV /dev/sdd                  VG freenas      lvm2 [500.00 GB / 0    free]
  PV /dev/sdc                  VG thecus       lvm2 [1010.00 GB /
1010.00 GB free]
  PV /dev/mapper/ddf1_RAIDp2   VG VolGroup00   lvm2 [931.25 GB / 0    free]
  Total: 3 [2.38 TB] / in use: 3 [2.38 TB] / in no VG: 0 [0   ]

[root at francois-pc ~]# lvscan
  ACTIVE            '/dev/freenas/500-gig' [500.00 GB] inherit
  ACTIVE            '/dev/VolGroup00/LogVol00' [925.62 GB] inherit
  ACTIVE            '/dev/VolGroup00/LogVol01' [5.62 GB] inherit




>
>>
>>
>>
>> How do I actually create a 500GB volume?
>
> You can't. There is one extent's worth of space used for LVM meta data.
>
>>
>>
>>
>>
>
> --
> Robert Heller             -- 978-544-6933 / heller at deepsoft.com
> Deepwoods Software        -- http://www.deepsoft.com/
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-- 
Kind Regards
Rudi Ahlers
SoftDux

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