Veritas File System
Veritas Filesystem ( VxFS) is an extent based, intent logging file system. VxFS is geared toward Unix environments that require high performance and availability and deal with large amounts of data.
VxFS features: -
The VxFS version 4 disk layout divides the entire file system space into fixed sized allocation units. The first allocation unit starts at block zero and all allocation units 32K blocks. All structural information are contained in files. So expanding the filesystem structures simply requires extending the appropriate structural files. All version 4 structural files reside in the structural fileset.
The structural files in version 4 disk layout are:
| Object location Table file | Contains the object location table (OLT). The OLT, which referenced from the superblock is used to locate the other structural files. |
| Label File | Encapsulates the super-block and super-block replicas. Although the primary location of the super-block is known, the label file can be used to locate upper-block copies ifthere is structural damage to the filesystem. |
| Device File | Records device information such as volume length and volume label and contains pointers to other structural files. |
| Fileset Header File | Hold
information on a per- fileset basis. This may include the inode of the
fileset’s inode list file, the maximum number of inodes allowed, an
indication of whether the filesystem supports large files and the inode
number of quotas file if the filesetsupports quotas. |
| Inode List File | Both the structural fileset and the primary fileset have their own inode lists which are stored in inode list files. Increasing the number of inodes involves increasing the size of the file after expanding the inode allocation unit file. |
| Inode Allocation Unit File | Hold the free inode map, extended operations map and a summary of the inode resources. |
| Log File | Maps the block used by the filesystem intent log. |
| Extent Allocation Unit State File | Indicates the allocation state of each AU by defining whether each AU is free allocated as a whole (no bitmaps allocated) or expanded, in which case the bitmaps associated with each AU determine which extents are allocated. |
| Extent Allocation Unit Summary File | Contains the AU summary for each allocation unit, which contains the number of free extents of each size. The summary for an extent is created only when an allocation unit is expanded for use. |
| Free Extent Map File | Contains the free extent maps for each of the allocation units. |
| Quotas File | If the filesystem supports quotas, there is a quotas file, which is used to track the resources allocated to each user. |
The mkfs command creates veritas filesystems by writing to a special character device.
To create a file system:
mkfs [-F vxfs] [ generic_option] [-o special_option] device [size]
generic_option Options common to other filesystem types
special_option Options specific to VxFS filesystem
device disk device or Veritas volume
size the size in sectors
example:
| mkfs –F vxfs –o largefiles /dev/vx/rdsk/appdg/samba_vol # Option largefiles set |
output:
version 4 layout |
Note: you do not get the super-block output list as in newfs
| Mount a VXFS filesystem | mount –F vxfs –o largefiles /dev/vx/rdsk/appdg/samba_vol /samba |
| Umount a VXFS filesystem | umount /samba |
To see information on a filesystem:
mount -v |
Use the fstyp command to identify a filesystem type:
fstyp -v /dev/vx/dsk/appdg/samba_vol or /dev/vx/rdsk/appdg/samba_vol |
Use the fsadm command to shrink/grow a filesystem:
| Shrink a filesystem | /usr/lib/vxfs/fsadm -b 102400 /samba |
| Grow a filesystem | /usr/lib/vxfs/fsadm -b 204800 /samba |
Use the fsadm ro reorganise (defrag) a filesystem:
| Report on extent fragmentation: | /usr/lib/fs/vxfs/fsadm -E /samba |
| Report on directory fragmentation: | /usr/lib/fs/vxfs/fsadm -D /samba |
| Reorganise extents: | /usr/lib/fs/vxfs/fsadm -e /samba |
| Reorganise directories: | /usr/lib/fs/vxfs/fsadm -d /samba |
Use the mount command to create the snap shot filesystem then use vxdump (or tar, dd, cpio) to backup the filesystem to tape:
| Create the snapshot filesystem: | mount -F vxfs -o snapof=/dev/vx/dsk/appdg/samba_vol snap,size=208400 \ |
| Backup the filesystem: | vxdump -cf /dev/rmt/1cbn /snapshot |
| Restore the filesystem (to /restore filesystem): | vxrestore -vx /restore |
| Turn on a quota for a filesystem (make sure filesystem has been mounted with quota option): | vxquotaon <mount_point> Note: a file will be created called quotas (it's a text file) |
| To setup a users quota | vxedquota <username> |
| To view a users quota: | vxquota -v <username> |
| To turn off quota on a filesystem: | vxquotaoff <mount_point> Note: The quota file is not removed. |