super block

[wish_1]

Dear all

New to this.

how many super-blocks are there, if courrpted how to recove the same.

another thing i want to know if i have given one HDD how to create the vols. in the same--- pleas. mail the step by step process.

thanks in adv
regards
wish

[LoC_1]

You can get the detailed instructions at the following url
http://docs.hp.com/en/B2355-90672/ch03s10.html

[Devender Khatana · Accepted solution]

Hi,

The first alternative super block is 32.Here is the documentation for finding out alternate super-blocks /magic numbers and recovering file systems from them.

http://publib16.boulder.ibm.com/pseries/en_US/infocenter/howto/HT_baseadmn_badmagnumb.htm

The small C program in this thread will also find this for you in case of non vxfs file systems

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=108262

For adding lvols/file systems onto the disk you have two options either add disk to existing VG or create new vg.
Suppose /dev/rdsk/cxtydz is the disk

Choice 1 - Add to existing VG

#pvcreate /dev/rdsk/cxtydz

(Use -f option if not done without it)
#vgextend /dev/existing_vgname /dev/dsk/cxtydz

#lvcreate -L xxxx /dev/exitsing_vgname
#newfs -F vxfs /dev/existing_vgname/rlvol?

Where existing_vgname is the VG you wish this disk to be added to,rlvol? is the new LVOL created by lvcreate command and xxxx is the required file systems size in MBs.

The same procedure can be repeated for more than one LVOLs.

Choice 2 - Add using new VG.

#pvcreate /dev/rdsk/cxtydz

(Use -f option if not done without it)
#mkdir /dev/newvgname
#mknod group c 64 0x??0000
#vgcreate /dev/newvgname /dev/dsk/cxtydz

#lvcreate -L xxxx /dev/newvgname
#newfs -F vxfs /dev/existing_vgname/rlvol?

Where newvgname is the VG you wish to create,rlvol? is the new LVOL created by lvcreate command, ?? is the unique minor number available find existing ones by "ll /dev/*/group" and xxxx is the required file systems size in MBs.

The same procedure can be repeated for more than one LVOLs.

HTH,
Devender

[Chauhan Amit]

a) HFS is the legacy file system used with HP-UX. Although JFS is used in the newer versions of HP-UX, HFS is still in use for the /stand file system and is supported on all HP-UX releases. The first 8 Kbytes of all HFS file systems contain the HFS superblock, which contains general information and pointers to the metadata area as already discussed. HFS contains more than one copy of the superblock, and the locations of these redundant copies are recorded in the /var/adm/sbtab file. If the main superblock is damaged, it can be recovered from one of the backup copies.

Option that can be used with the fsck command to recover Superblock.

-b Tells fsck to use an alternate superblock. The alternate superblocks are listed in the /var/adm/sbtab file. If this file is not accessible, use number 16, which is always the first alternate superblock (HFS only).

#man fsck (For More details)

b) JFS also maintains multiple copies of the superblock, but these are not stored in any file. JFS keeps a record of these copies automatically. JFS keeps a record of all transactions to the file system metadata area in an intent log. The intent log is used for system recovery in case of a system crash. If a file system update is completed successfully, a "done record" is written to the intent log showing that this update request was successful. In case of a system crash, the intent log is consulted and the file system brought to the stable state by removing all unsuccessful transactions with the help of the intent log.

Hope this is helpful. Procedure for creating File system is already provided above.

-Amit