Showing posts with label VxVM. Show all posts
Showing posts with label VxVM. Show all posts

Tuesday, October 7, 2014

Disk Metadata : Superblock, Directory and Inodes

Metadata
Filesystem blocks are user for 2 purposes : To store User data and Metadata
  • User data - stores actual data contained in files
  • Metadata - stores file system structural information such as superblock, inodes, directories
Metadata describes the structure of the file system. Most common metadata structure are superblock, inode and directories.

Superblocks
Every FS has a superblock which contains info about filesystems such as :
  • File system type
  • Size
  • Status
  • Information about other metadata structures
    • For filesystems with 1k blocksizes, a backup superblock can be found at block 8193
    • For filesystems with 2k blocksizes, at block 16384
    • For 4k blocksizes, at block 32768.
List backup superblocks:
# dumpe2fs /dev/hda3 | grep -i superblock

If Superblock  is corrupted, restore with backup :
# e2fsck -f -b 8193 /dev/sda3
 
Inode
 
 An inode is a data structure on a Linux Unix FS which stores stores basic information about a regular file, directory, or other file system objects.  

Thursday, October 10, 2013

How to configure Veritas Volume Manager VxVM 6.0.2

The disks should be discovered by OS before it can be added to Veritas Volume Manager.


1. List the disks detected by VxVM.

# vxdisk -o alldgs list


Eg :

[root@rhel61 ~]# vxdisk -o alldgs list
DEVICE       TYPE            DISK         GROUP        STATUS
sda          auto:none       -            -            online invalid
sdb          auto:none       -            -            online invalid
sdc          auto:cdsdisk    mydg01       mydg         online
sdd          auto:cdsdisk    mydg02       mydg         online
[root@rhel61 ~]#

sda and sbd are not configured / initialized for VxVM; where as sdc and sdd are initialized and added to a disk group.


2. Initialize disks.

vxdisksetup -i [attributes]

# vxdisksetup -i sdc
# vxdisksetup -i emc0_dd1

Initializing a disk will create Privae and Public regions in the disks, Meta data is stored in private region and public reagion is available for general purpose data usage. 32 MB is reserved for private region.