[linux-lvm] large logical volumes
Guido Vettoretti
guido at atmosp.physics.utoronto.ca
Fri Apr 29 20:35:02 UTC 2005
Someone answered my reponse! Thanks
Anyway. I've sorted things out. I've manage to set up a fairly large
RAID fs on and intel xeon 32-bit server running RHEL4.
As you suggest the solution was to go to a new fs (I chose XFS as Reiser
seemed to behave strangely with LVM and the large filesystem). I just
had to rebuild the kernel with xfs support. Things are running smoothly
right now.
In case anyone is interested there seem to be some limitations:
32-bit machines:
ext3 : 2Tb (I managed to create a 4TB fs for some reason)
xfs : 16 Tb
reiser : 16Tb
64-bit:
ext3: 2Tb (? not sure about this one)
xfs and reiser: very large (> million Tb)
One of the hardware support people said there was a 2Tb limit on the
SCSI protocol (not sure about this), so I had to use LVM to create the
large volume from a subset of RAID volumes even though the native
capacity of the RAID unit was 16Tb. So the process was to divide and
recollect the RAID volumes using LVM and xfs.
Cheers,
Guido
Myrddin Emrys wrote:
>Looks like you never got a response. I hardly consider myself
>qualified, but have you considered increasing the block size? The
>other option, have you tried a different filesystem? Different fs have
>different limitations... what you're describing appears to be a
>limitation of ext2fs, not LVM. Have you considered XFS or ReiserFS?
>
>On 3/30/05, Guido Vettoretti <g.vettoretti at utoronto.ca> wrote:
>
>
>>Hello,
>>
>>I'm trying to set up a large logical volume (13.1 TB) on a RHEL 4.0
>>server. I have 8 scsi devices of 1.8Tb each.
>>
>>When I try to do a 'mkfs' and set up a large disk I get limited to 4Tbytes.
>>This command creates a smaller filesystem then
>>[root at cyclone ~]# lvcreate -l 1287525 -i 3 -n lvol0 vol0
>>this one.
>>[root at cyclone ~]# lvcreate -l 1000000 -i 3 -n lvol0 vol0
>>
>>It seems that there is a limit on the number of block groups of 32768
>>and blocks per group of 32768.
>>My block size is 4096
>>so I can only get an LV of 4096*32768*32768 = 4TB.
>>
>>I tried modifying the PE size on the volume group, but I'm still having
>>problems.
>>
>>Can anyone help please?
>>
>>Thanks
>>Guido
>>---------------
>>[root at cyclone ~]# mkfs -t ext3 /dev/vol0/lvol0
>>mke2fs 1.35 (28-Feb-2004)
>>max_blocks 4294967295, rsv_groups = 0, rsv_gdb = 1024
>>Filesystem label=
>>OS type: Linux
>>Block size=4096 (log=2)
>>Fragment size=4096 (log=2)
>>512016384 inodes, 1024002048 blocks
>>8250429 blocks (0.81%) reserved for the super user
>>First data block=0
>>Maximum filesystem blocks=1027604480
>>31251 block groups
>>32768 blocks per group, 32768 fragments per group
>>16384 inodes per group
>>Superblock backups stored on blocks:
>> 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632,
>>2654208,
>> 4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
>> 102400000, 214990848, 512000000, 550731776, 644972544
>>
>>Here is the entire process I typed:
>>------------------------------------------------------------------------------
>>
>>[root at cyclone ~]# pvcreate /dev/sdc1 /dev/sdd1 /dev/sde1
>> Physical volume "/dev/sdc1" successfully created
>> Physical volume "/dev/sdd1" successfully created
>> Physical volume "/dev/sde1" successfully created
>>[root at cyclone ~]# pvscan
>> /dev/cdrom: open failed: No medium found
>> PV /dev/sda2 VG VolGroup00 lvm2 [34.06 GB / 0 free]
>> PV /dev/sdb1 VG VolGroup00 lvm2 [34.16 GB / 0 free]
>> PV /dev/sdc1 lvm2 [1.64 TB]
>> PV /dev/sdd1 lvm2 [1.64 TB]
>> PV /dev/sde1 lvm2 [1.64 TB]
>> Total: 5 [4.98 TB] / in use: 2 [68.22 GB] / in no VG: 3 [4.91 TB]
>>[root at cyclone ~]# vgcreate vol0 /dev/sd[c-e]1
>> Volume group "vol0" successfully created
>>[root at cyclone ~]# vgdisplay
>> --- Volume group ---
>> VG Name vol0
>> System ID
>> Format lvm2
>> Metadata Areas 3
>> Metadata Sequence No 1
>> VG Access read/write
>> VG Status resizable
>> MAX LV 0
>> Cur LV 0
>> Open LV 0
>> Max PV 0
>> Cur PV 3
>> Act PV 3
>> VG Size 4.91 TB
>> PE Size 4.00 MB
>> Total PE 1287525
>> Alloc PE / Size 0 / 0
>> Free PE / Size 1287525 / 4.91 TB
>> VG UUID fQ7cKh-FVnl-NglQ-jimv-RsZK-dU5j-zYKIcG
>>
>>[root at cyclone ~]# lvcreate -l 1287525 -i 3 -n lvol0 vol0
>> Using default stripesize 64KB
>> Logical volume "lvol0" created
>>[root at cyclone ~]# lvdisplay
>> --- Logical volume ---
>> LV Name /dev/vol0/lvol0
>> VG Name vol0
>> LV UUID c2MADb-BoAO-lhl3-3ukj-XfyQ-K8L0-cxcIlw
>> LV Write Access read/write
>> LV Status available
>> # open 0
>> LV Size 4.91 TB
>> Current LE 1287525
>> Segments 1
>> Allocation inherit
>> Read ahead sectors 0
>> Block device 253:2
>>
>>[root at cyclone ~]# mkfs -t ext3 /dev/vol0/lvol0
>>mke2fs 1.35 (28-Feb-2004)
>>max_blocks 4294967295, rsv_groups = 0, rsv_gdb = 1024
>>Filesystem label=
>>OS type: Linux
>>Block size=4096 (log=2)
>>Fragment size=4096 (log=2)
>>122355712 inodes, 244683776 blocks
>>12234188 blocks (5.00%) reserved for the super user
>>First data block=0
>>Maximum filesystem blocks=247463936
>>7468 block groups
>>32768 blocks per group, 32768 fragments per group
>>16384 inodes per group
>>Superblock backups stored on blocks:
>> 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632,
>>2654208,
>> 4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
>> 102400000, 214990848
>>
>>_______________________________________________
>>linux-lvm mailing list
>>linux-lvm at redhat.com
>>https://www.redhat.com/mailman/listinfo/linux-lvm
>>read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>>
>>
>>
>
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>read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>
>
>
>
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