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Does /var/adm/crash have to be mounted on root vg (vg00)?

Ameer Dixit
Advisor

Does /var/adm/crash have to be mounted on root vg (vg00)?

Does the crash space have to be mounted on the root volume group? I would think so, since if the system crashes, upon reboot it will try to copy the dump to the crash space, and this will happen before any other volume groups are activated.

I read the documentation, but just wanted to confirm.

Thanks!
8 REPLIES
Michael Steele_2
Honored Contributor

Re: Does /var/adm/crash have to be mounted on root vg (vg00)?

Hi

Send me your /etc/fstab file and vgdisplay -v vg00

What you are asking you should know. Is crash a mount point or a sub directory of /var? So check for a log vol assicated to crash.
Support Fatherhood - Stop Family Law
Ameer Dixit
Advisor

Re: Does /var/adm/crash have to be mounted on root vg (vg00)?

Hello Michael,

There is no seperate mount point for /var/adm/crash on the system now, so any crash would currently go to /var. /var doesn't have enough space to handle the recommended size for a crash.

There is no more free space in /vg00 (internal disk), and I don't think I can create an LV on another VG and mount /var/adm/crash there and have the system write a crash to that location.

I'm trying to confirm if I'm correct.
TTr
Honored Contributor

Re: Does /var/adm/crash have to be mounted on root vg (vg00)?

You can disble the saving of the crashdump by editing /etc/rc.config.d/savecrash. If you need a crash dump, it will still be in the swap/dump volume after the server boots up. If the server does NOT run out of memory and does not swapp to disk, the crash dump will remain intact on the swap/dump volume. You then find some disk space somewhere and you manually run the savecrash command if needed.
Michael Steele_2
Honored Contributor

Re: Does /var/adm/crash have to be mounted on root vg (vg00)?

Hi

Well check for free space on your box. Please post these reports:

vgdisplay -v vg00
ioscan -funC disk

Thanks!
Support Fatherhood - Stop Family Law
Nath_3
Frequent Advisor

Re: Does /var/adm/crash have to be mounted on root vg (vg00)?

Hi Ameer,

As far as i have worked and know that the default Hp-ux will have /var/adm/crash as a default Mount point in /vg00.

It is recommended to have the /var/adm/crash on /vg00.

what if the /var fills out? Server hangs and somes times goes for toss.

It is always recommended.

Thanks
Ravi
VK2COT
Honored Contributor

Re: Does /var/adm/crash have to be mounted on root vg (vg00)?

Hello,

Never keep /var/adm/crash in the same logical volume as /var/. Too easy to make
a mess and fill critical file system like
/var.

In fact, when I design HP-UX servers, three
separate file systems are part of critical
setup:

/var
/var/tmp
/var/adm/crash

... and if OVO is used, I even add

/var/opt/perf
/var/opt/OV

The good practice actually brings different
view on how to set up crash areas,
especially on servers with large amount of RAM:

a) Separate dump from swap (default is they
are together on primary swap);

b) Disable savecrash at boot time and
save around 50% time for a reboot when
crash happens;

c) Create separate logical volume (it can
be in ANY volume group, not necessarily
root VG or DG, depending on if you use
LVM or VxVM);

d) Once you recover from a crash, you
can manually start savecrash process.

That makes your SLA much better and
customer happier!

Just think what happens during crash recovery
on a server with, say 256 GB RAM.
It might take along time to save pages into dump/swap on the way "down", and taking
a lot of time exporting those raw pages into, say, /var/adm/crash" on the way "up".
Waste of time and customer will
certainly not be happy waiting so long
for a server to come on-line.

Cheers,

VK2COT
VK2COT - Dusan Baljevic
Raj D.
Honored Contributor

Re: Does /var/adm/crash have to be mounted on root vg (vg00)?

Ameer Dixit,
Best Practice to have :
/var/adm/crash as a "separate filesystem " say lvol10 , in vg00 . (16GB space), if you have 16GB primary swap configured.


# To check dump size required, in case of a crash , use:
# /sbin/crashconf -v
-Look for "Total Pages included in the dump" , multiply by 4K , i.e = dump size you need ., including /var/adm/crash space.

- If you need additional dump space, add more dump lv :
You can specify up to 32 different dump devices. These LVs must not contain a filesystem and have to belong to the rootVG (/dev/vg00).

then and add in fstab and activate using crashconf -a .
-Check again using crashconf -v.



A good description of the 11.X dump process can be found in the â System Crash Dump White
Paperâ located at /usr/share/doc/sys_crash.txt on every UX 11.X system.



Hth.
Raj.
" If u think u can , If u think u cannot , - You are always Right . "
Ameer Dixit
Advisor

Re: Does /var/adm/crash have to be mounted on root vg (vg00)?

It appears that /var/adm/crash would have to be mounted on vg00 since no one has said otherwise. Thanks for your help.