Volume Group Size
Hi all,
I cant find information about the maximum volume group size in the current 2.4 series kernel.
Id like to be able to join 2 1.75Tb raid arrays into 1 3.5Tb array. Is this possible?
Cheers in advance
Stuart
Quoted 5 lines · Stuart Fox
I cant find information about the maximum volume group size in the current 2.4 series kernel.
Id like to be able to join 2 1.75Tb raid arrays into 1 3.5Tb array. Is this possible?
No, there is a limit of 2TB for all block devices in 2.4 kernels. With 2.5, there is a "large block device" configure option that lets you have larger block devices. There is apparently also a patch to support this on 2.4 kernels, but AFAIK it is not very widely used/tested.
Cheers, Andreas
--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://www-mddsp.enel.ucalgary.ca/People/adilger/
Quoted 11 lines · Andreas Dilger
Quoted 5 lines · Stuart Fox
I cant find information about the maximum volume group size in the current 2.4 series kernel.
Id like to be able to join 2 1.75Tb raid arrays into 1 3.5Tb array. Is this possible?
No, there is a limit of 2TB for all block devices in 2.4 kernels. With 2.5, there is a "large block device" configure option that lets you have larger block devices. There is apparently also a patch to support this on 2.4 kernels, but AFAIK it is not very widely used/tested.
The question was regarding volum goups, not logical volums.
So, correct me if I'm wrong, but I think the answer is yes, you will be able to join 2 1.75 Tb volume groups into a single 3.5 Tb volum group, if only an apropriate extent-size was set on VG-creation.
However, each Logical Volum in the Volum-Group need to be smaller than 2 TB.
AFAIK the "large block device" feature in 2.5 does not enable > 2TB logical volumes - it only fixes the general block-device layer, md and the scsi-subsystem. At least that used to be the case - maybe someone knows if it has changed?
Signature · 2 lines
Ragnar Kjørstad Zet.no
Quoted 29 lines · Andreas Dilger
Quoted 5 lines · Stuart Fox
Quoted 1 line
I cant find information about the maximum volume group size in the
current
Quoted 2 lines
2.4 series kernel.
Quoted 7 lines
Quoted 2 lines
Id like to be able to join 2 1.75Tb raid arrays into 1 3.5Tb array. Is this possible?
No, there is a limit of 2TB for all block devices in 2.4 kernels. With 2.5, there is a "large block device" configure option that lets you have larger block devices. There is apparently also a patch to support this on 2.4 kernels, but AFAIK it is not very widely used/tested.
The question was regarding volum goups, not logical volums.
So, correct me if I'm wrong, but I think the answer is yes, you will be able to join 2 1.75 Tb volume groups into a single 3.5 Tb volum group, if only an apropriate extent-size was set on VG-creation.
However, each Logical Volum in the Volum-Group need to be smaller than 2 TB.
AFAIK the "large block device" feature in 2.5 does not enable > 2TB logical volumes - it only fixes the general block-device layer, md and the scsi-subsystem. At least that used to be the case - maybe someone knows if it has changed?
Quoted 4 lines
--
Ragnar Kj�rstad
Zet.no
Thanks for the quick replies.
It actually applied to both one vg with one lv of 3.5Tb. Guess I'll have to find another way.
Cheers
Stuart
Quoted 13 lines · Ragnar Kjørstad
Quoted 11 lines · Andreas Dilger
Quoted 5 lines · Stuart Fox
I cant find information about the maximum volume group size in the current 2.4 series kernel.
Id like to be able to join 2 1.75Tb raid arrays into 1 3.5Tb array. Is this possible?
No, there is a limit of 2TB for all block devices in 2.4 kernels. With 2.5, there is a "large block device" configure option that lets you have larger block devices. There is apparently also a patch to support this on 2.4 kernels, but AFAIK it is not very widely used/tested.
Quoted 5 lines
The question was regarding volum goups, not logical volums.
So, correct me if I'm wrong, but I think the answer is yes, you will be able to join 2 1.75 Tb volume groups into a single 3.5 Tb volum group, if only an apropriate extent-size was set on VG-creation.
The limitation for the size of a volume-group is a little obscure. The volume-group metadata (for LVM1 volume-groups - LVM2 format is probably different) stores the total number of PEs in the group as a 32-bit number. Thus, you are limited to 2^32 total extents. With a PE size of 4 MB, this is 2^54 bytes, or 16 exabytes (adjust accordingly for a different PE size).
Quoted 7 lines
However, each Logical Volum in the Volum-Group need to be smaller than 2 TB.
AFAIK the "large block device" feature in 2.5 does not enable > 2TB logical volumes - it only fixes the general block-device layer, md and the scsi-subsystem. At least that used to be the case - maybe someone knows if it has changed?
Again, the LVM1 format uses a 32-bit number to record the size (in sectors) of each LV. So the 2 TB limitation still exists. However, the metadata also records the number of extents allocated to the LV, so the tools *could* be written to ignore the lv-size field and always calculate based on the number of allocated extents. This would push the limit up to pe_size * 2^32 bytes, but would of course break backwards-compatibility with older tools (not sure if that really matters).
Signature · 3 lines
Kevin Corry [email protected] http://evms.sourceforge.net/