Storage Foundation 7.4.1 Administrator's Guide - Linux

To show the difference between Storage Checkpoints

1. Create a file system and mount it on /mnt0, as in the following example:

   # mkfs -t vxfs /dev/vx/rdsk/dg1/test0

   version 14 layout
   62914560 sectors, 31457280 blocks of size 1024, log size 65536 blocks
   rcq size    2048 blocks
   largefiles  supported
   maxlink     supported
   WORM not supported

   size  65536 blocks, largefiles supported
   # mount -t vxfs /dev/vx/dsk/dg1/test0 /mnt0

2. Create a small file with a known content, as in the following example:

   # echo "hello, world" > /mnt0/file

3. Create a Storage Checkpoint and mount it on /mnt0@5_30pm, as in the following example:

   # fsckptadm create ckpt@5_30pm /mnt0
   # mkdir /mnt0@5_30pm
   # mount -t vxfs -o ckpt=ckpt@5_30pm \
     /dev/vx/dsk/dg1/test0:ckpt@5_30pm  /mnt0@5_30pm

4. Examine the content of the original file and the Storage Checkpoint file:

   # cat /mnt0/file
   hello, world
   # cat /mnt0@5_30pm/file
   hello, world

5. Change the content of the original file:

   # echo "goodbye" > /mnt0/file

6. Examine the content of the original file and the Storage Checkpoint file. The original file contains the latest data while the Storage Checkpoint file still contains the data at the time of the Storage Checkpoint creation:

   # cat /mnt0/file
   goodbye
   # cat /mnt0@5_30pm/file
   hello, world

7. Unmount the Storage Checkpoint, convert the Storage Checkpoint to a nodata Storage Checkpoint, and mount the Storage Checkpoint again:

   # umount /mnt0@5_30pm
   # fsckptadm -s set nodata ckpt@5_30pm /mnt0
   # mount -t vxfs -o ckpt=ckpt@5_30pm \
   /dev/vx/dsk/dg1/test0:ckpt@5_30pm /mnt0@5_30pm

8. Examine the content of both files. The original file must contain the latest data:

   # cat /mnt0/file
   goodbye

   You can traverse and read the directories of the nodata Storage Checkpoint; however, the files contain no data, only markers to indicate which block of the file has been changed since the Storage Checkpoint was created:

   # ls -l /mnt0@5_30pm/file
   -rw-r--r--   1 root     other 13 Jul 13 17:13 \
   # cat /mnt0@5_30pm/file
   cat: /mnt0@5_30pm/file: Input/output error