The maximum size of a VxVM sliced or simple disk with DOS Label is 2TB

Article:HOWTO75129  |  Created: 2012-04-25  |  Updated: 2012-07-21  |  Article URL http://www.symantec.com/docs/HOWTO75129
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The DOS Label has a maximum size limit of 2TB (actually just a bit less than 2TB, 2047.99GB).    Both Linux and VxVM (Veritas Volume Manager) are constrained by this limitation.    As a result the LUN size of a sliced disk or simple disk using DOS label on Linux cannot be greater than or equal to 2TB.

Try running fdisk on a multi-terabyte LUN, fdisk will show this limitation.

# fdisk /dev/vdm
....
WARNING: The size of this disk is 5.5 TB (5497558138880 bytes).
DOS partition table format can not be used on drives for volumes larger than (2199023255040 bytes) for 512-byte sectors.
Use parted(1) and GUID partition table format (GPT).
......

2199023255040 bytes is equal to 4294967295 sector or 2047.99 GB.


When performing Dynamic LUN Expansion (DLE), VxVM can expand the LUN size up to this limit.   The following is an example of the DLE operation.

1. There are two disks in the diskgroup.

virtio0_8    auto:sliced     adg02        adg          online
virtio0_13   auto:sliced     adg01        adg          online    <<< LUN to be expanded

2. LUN virtio0_13 is expanded to 1.9TB on the storage side.

# fdisk -lu /dev/vx/rdmp/virtio0_13
Disk /dev/vx/rdmp/virtio0_13: 2040.1 GB, 2040109465600 bytes     <<< expanded to 1.9TB
16 heads, 63 sectors/track, 3952965 cylinders, total 3984588800 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x40d7f80b
                   Device Boot      Start         End      Blocks   Id  System
/dev/vx/rdmp/virtio0_13p4              63     4185215     2092576+   5  Extended         <<< original DOS label and partition table
/dev/vx/rdmp/virtio0_13p5             315       66149       32917+  7f  Unknown
/dev/vx/rdmp/virtio0_13p6           66213     4185215     2059501+  7e  Unknown


# vxdisk list virtio0_13
Device:    virtio0_13
devicetag: virtio0_13
type:      auto
hostid:    rhel6vm1
disk:      name=adg01 id=1335408904.130.rhel6vm1
group:     name=adg id=1335408970.137.rhel6vm1
info:      format=sliced,privoffset=1,pubslice=6,privslice=5       <<< sliced disk
flags:     online ready private autoconfig autoimport imported
pubpaths:  block=/dev/vx/dmp/virtio0_13s6 char=/dev/vx/rdmp/virtio0_13s6
privpaths: block=/dev/vx/dmp/virtio0_13s5 char=/dev/vx/rdmp/virtio0_13s5
guid:      -
udid:      QEMU%5FVIRTIO%5FVirtIO%5F%2Fdev%2Fvdn
site:      -
version:   2.1
iosize:    min=512 (bytes) max=1024 (blocks)
public:    slice=6 offset=0 len=4119003 disk_offset=66213          <<< original public region size
private:   slice=5 offset=1 len=65578 disk_offset=315
update:    time=1335408973 seqno=0.7
ssb:       actual_seqno=0.0
headers:   0 248
configs:   count=1 len=51612
logs:      count=1 len=4096
Defined regions:
 config   priv 000017-000247[000231]: copy=01 offset=000000 enabled
 config   priv 000249-051629[051381]: copy=01 offset=000231 enabled
 log      priv 051630-055725[004096]: copy=01 offset=000000 enabled
Multipathing information:
numpaths:   1
vdn             state=enabled


# vxscsi -g /dev/vx/rdmp/virtio0_13
geometry of /dev/vx/rdmp/virtio0_13: nhead=255 nsect=378 ncyl=41338 sectsz=512 rpm=3600 cap=3984588800

3. Run vxdisk rezie to expand the LUN.

# vxdisk -g adg resize adg01

4. Now the DOS label is updated to 1.9TB.

# fdisk -lu /dev/vx/rdmp/virtio0_13
Disk /dev/vx/rdmp/virtio0_13: 2040.1 GB, 2040109465600 bytes     
1 heads, 63 sectors/track, 63247441 cylinders, total 3984588800 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x40d7f80b
                   Device Boot      Start         End      Blocks   Id  System
/dev/vx/rdmp/virtio0_13p4              63  3984377102  1992188520    5  Extended       <<< new DOS label and partition table
/dev/vx/rdmp/virtio0_13p5             315       66149       32917+  7f  Unknown
/dev/vx/rdmp/virtio0_13p6           66213  3984377039  1992155413+  7e  Unknown

# vxdisk list virtio0_13
Device:    virtio0_13
devicetag: virtio0_13
type:      auto
hostid:    rhel6vm1
disk:      name=adg01 id=1335408904.130.rhel6vm1
group:     name=adg id=1335408970.137.rhel6vm1
info:      format=sliced,privoffset=1,pubslice=6,privslice=5        <<< sliced disk
flags:     online ready private autoconfig autoimport imported
pubpaths:  block=/dev/vx/dmp/virtio0_13s6 char=/dev/vx/rdmp/virtio0_13s6
privpaths: block=/dev/vx/dmp/virtio0_13s5 char=/dev/vx/rdmp/virtio0_13s5
guid:      -
udid:      QEMU%5FVIRTIO%5FVirtIO%5F%2Fdev%2Fvdn
site:      -
version:   2.1
iosize:    min=512 (bytes) max=1024 (blocks)
public:    slice=6 offset=0 len=3984310827 disk_offset=66213       <<< new public region size
private:   slice=5 offset=1 len=65834 disk_offset=315
update:    time=1335409109 seqno=0.8
ssb:       actual_seqno=0.0
headers:   0 248
configs:   count=1 len=51612
logs:      count=1 len=4096
Defined regions:
 config   priv 000017-000247[000231]: copy=01 offset=000000 enabled
 config   priv 000249-051629[051381]: copy=01 offset=000231 enabled
 log      priv 051630-055725[004096]: copy=01 offset=000000 enabled
Multipathing information:
numpaths:   1
vdn             state=enabled


Please note that there could be a potential data corruption problem with DLE as tracked by the following Etrack incident.

Etrack 2557984 - VxDMP size in /proc/partitions table doesn't match with the vxdisk list <dmpnode>

Please apply 5.1SP1RP2P2HF15 to fix the above etrack incident before performing any DLE operations.


If it is required to expand the LUN to over 2TB, please following the instruction in the related article TECH136240 to convert the disk to a CDS disk and perform the DLE on the converted CDS disk.

 




Article URL http://www.symantec.com/docs/HOWTO75129


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