topic Re: Spurious characters in LVMTAB in Operating System - HP-UX

Spurious characters in LVMTAB

Andy Smith_1 — Thu, 27 Jun 2002 09:34:02 GMT

are the spurious characters in this lvmtab the result of someone trying to vi it, or do they have a function and if so what ?
/dev/vg00
X]@*1
/dev/dsk/c3t5d0
/dev/dsk/c1t3d0
/dev/vg02
X]@*7j
/dev/dsk/c3t6d0
/dev/dsk/c1t5d0
/dev/vg03
X]@*:
/dev/dsk/c1t6d0
/dev/dsk/c0t6d0

Re: Spurious characters in LVMTAB

T G Manikandan — Thu, 27 Jun 2002 09:38:11 GMT

Hello

The type of the lvmtab is 'data'.
YOu cannot do a vi into that.

#strings /etc/lvmtab
should show you the contents.

Thanks

Re: Spurious characters in LVMTAB

steven Burgess_2 — Thu, 27 Jun 2002 09:39:31 GMT

Hi Andy

I havee seen this on a couple of our boxes. Not sure why it happens though

You can recreate lvmtab by moving it to lvmtab.bak and performing a

vgscan -a

This will recreate lvmtab. The only problem being that it won't be in descending order by volume group

man vgscan

for more options

Hope this helps

Steve

Re: Spurious characters in LVMTAB

steven Burgess_2 — Thu, 27 Jun 2002 09:42:02 GMT

Hi

T G

Have seen this even after

strings /etc/lvmtab

What do you think may be the cause ?

Steve

Re: Spurious characters in LVMTAB

T G Manikandan — Thu, 27 Jun 2002 09:47:01 GMT

Yes,
you have the volume group with the physical disk information in it.It has the table where the volume groups and the associated physical volumes in each group.
If sometime your lvmtab file is corrupt then
you should do a vgscan -a
to rebuild the lvmtab file.

Re: Spurious characters in LVMTAB

Bill McNAMARA_1 — Thu, 27 Jun 2002 10:04:19 GMT

These characters are not a problem.
Your lvmtab is not corrupt.
files /etc/lvmtab reports the file is data.

strings /etc/lvmtab extracts the printable characters.. which do not always report just device files.

A vgscan recreation can mess up your pvlinks configuration(alternate paths) very easily causing serious perf degradation.. make sure you know what you're doing.

Later,
Bill

Re: Spurious characters in LVMTAB

Bill McNAMARA_1 — Thu, 27 Jun 2002 10:07:06 GMT

Looking at your vg03 for example, vgscan will reconfigure it as:

/dev/dsk/c0t6d0
/dev/dsk/c1t6d0

the other vgs will also be swapped. vgscan recreates in numberical order of device file...

Later,
Bill

Re: Spurious characters in LVMTAB

Thierry Poels_1 — Thu, 27 Jun 2002 10:21:06 GMT

Hi,

/etc/lvmtab is NOT a textfile, and should be edited manually.

"strings /etc/lvmtab" will also show some rubbisch in many cases. "strings" only tries to filter out non-text data, but can never really know what is what.

regards,
Thierry.

Re: Spurious characters in LVMTAB

Shahul — Thu, 27 Jun 2002 11:00:47 GMT

Hi

lvmtab is not a text file. It normally contains some unreadable charecters. It is not because of somebody is doing vi. If U doubt like this it is always better to keep a copy of lvmtab. For seeing the contents of lvmtab

#strings /etc/lvmtab

Best of luck
Shahul

Re: Spurious characters in LVMTAB

James R. Ferguson — Thu, 27 Jun 2002 11:28:35 GMT

Hi Andy:

The /etc/lvmtab is a binary data file. As noted, 'strings /etc/lvmtab' will expose the printable characters. The file is not and should not be editted manually in any fashion.

The file actually contains the physical device paths for each volume group defined to the system. In addition, the VGID (Volume Group Identification) and some other state information about each volume group is recorded.

As Bill has aptly noted, do *not* capraciously run 'vgscan'. This may reorder the primary and alternate paths to a volume group leading to non-optimal performance. It is the order of the paths in /etc/lvmtab that determines which is a primary and which as an alternate (secondary) pvlink. For vg00, boot information may become incorrect due to reordering of devices following a 'vgscan'. See the 'vgscan' man pages for more information.

Regards!

...JRF...

Re: Spurious characters in LVMTAB

Carlos Fernandez Riera — Thu, 27 Jun 2002 11:36:31 GMT

NO problem....

That rare string is part of VGID, and it is recorded on all disks and lvmtab.

No problem.

Re: Spurious characters in LVMTAB

Rafael M. Ferreira — Thu, 27 Jun 2002 11:46:32 GMT

Andy Smith

You don??t open /etc/lvmtab file with vi because it is of the type data file

You can open this file with
strings /etc/lvmtab

Rafael