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configuring dump device and other questions

 
silusan
Regular Advisor

configuring dump device and other questions

 

The dump device we have in our servers is /dev/vg00/lvol2
crashconv -v/crashconf-l confirms it

 

Just wanted to check...is this not a recommendedconfiguration? setting lvol2 as dump device? if yes why? (question 1)
I understand lvol2 will be dumpdevice by default

 

I have these: 11.31 OS / vxfs / LVM
RAM 16GB, soon we will increase it to 32GB

 

if due to some reason...in my environment here, if i were asked to unconfigure swap (lvol2) as dump and set something else as dumpdevice..then i need to use space left in VG00..which is just 4GB
I dont want to use that left over space in vg00.

can i use /var/adm/crash as my dumpdevice instead of lvol2? (question 2)

 

/dev/vg00/lvol9    16777216   70376 15662798    0% /var/adm/crash

 

 

If yes, how do I do that? (question 3)

 

Another question is
crashconf -v output has this
Total pages included in dump:     606354

so this is how I calculated space needed for dump

Dumpsize = 606354x4KB=2425416KB = 2.3GB

2.3 x 1.2 = 2.77 GB

So..am I right in saying that 2.77 GB is what we need for a dump to happen completely? (question 4)

 

can you please suggest and help

 

thank you.

7 REPLIES
silusan
Regular Advisor

Re: configuring dump device and other questions

unable to attach..so pasting crashconf -v
o/p
# crashconf -v
Crash dump configuration has been changed since boot.

CLASS PAGES INCLUDED IN DUMP DESCRIPTION
-------- ---------- ---------------- -------------------------------------
UNUSED 3038384 no, by default unused pages
USERPG 412167 no, by default user process pages
BCACHE 60671 no, by default buffer cache pages
KCODE 9081 no, by default kernel code pages
USTACK 3091 yes, by default user process stacks
FSDATA 12 yes, by default file system metadata
KDDATA 594434 yes, by default kernel dynamic data
KSDATA 8817 yes, by default kernel static data
SUPERPG 66227 no, by default unused kernel super pages

Total pages on system: 4192884
Total pages included in dump: 606354

Dump compressed: ON

Dump Parallel: ON

DEVICE OFFSET(kB) SIZE (kB) LOGICAL VOL. NAME
------------ ------------ ------------ ------------ -------------------------
1:0x000000 2087776 16777216 64:0x000002 /dev/vg00/lvol2
------------
16777216
Dump device configuration mode is config_deprecated_mode.
Use crashconf -s option to change the mode.
#

Re: configuring dump device and other questions

>unable to attach

 

You may need to give it a .txt suffix.

silusan
Regular Advisor

Re: configuring dump device and other questions

thank you Dennis.... attaching now

Torsten.
Acclaimed Contributor

Re: configuring dump device and other questions

The default dump device is /dev/vg00/lvol2

Check with

# lvlnboot -v

...
Dump: lvol2 on: /dev/dsk/c2t0d0s2, 0
...

In case of a crash the memory will be dumped to this device, then compressed and stored in the crashconf directory.

In some cases you need to think about if you can life without a complete dump (imagine a SD2 with 4TB RAM!).

However, you may consider to increase the dump device by using ignite backup/restore.

Hope this helps!
Regards
Torsten.

__________________________________________________
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those who understand binary, and those who don't.

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silusan
Regular Advisor

Re: configuring dump device and other questions

yes...dev/vg00/lvol2 is default in our server too.

crashconf -v / crashconf -l / lvlnboot command outputs confirm it,

 

our design documents says - primary swap MUST NOT be used to receive crash dumps.

So I am looking for other places..

unfortunately, our VG00 is left with just 3.5Gb of free space.

 

RAM = 16GB

pri swap lvol2=16GB

additional (sec) swap = /dev/vgxx/lvolyy = 16GB

11.31 hpux

 

the image we used to deploy OS from ignite has /var/adm/crash too in it.

it will created automatically and its entries will be present in fstab by default.

I learnt that ..in this case /var/adm/crash(/dev/vg00/lvol9) isnt a raw device , so it cant be used to receive system crash dump.

 

so how do I go about this?

 

can I not use /var/adm/crash as dump device?

 

or my other idea is

reduce /var/adm/crash size from 16Gb to 8GB..thus freeing up some space from VG00 and used this freedup space in g00 to create an LV and use to receive dumps.

 

any suggestions please?

 

thank you

 

 

 

Torsten.
Acclaimed Contributor

Re: configuring dump device and other questions

Please understand that the system first dumps the memory contents to a raw device, then write these data to the filesystem. So you cannot use the same space for both tasks. To reduce the the filesystem used to store the filesystem, just delete your lvol9 and re-create it.

Hope this helps!
Regards
Torsten.

__________________________________________________
There are only 10 types of people in the world -
those who understand binary, and those who don't.

__________________________________________________
No support by private messages. Please ask the forum!

If you feel this was helpful please click the KUDOS! thumb below!   
silusan
Regular Advisor

Re: configuring dump device and other questions

thanks...so I cannot make /var/adm/crash to appear in crashconf -v output

 

so... will free up some space in VG00

create a new lvol in VG00

and will then configure this new lvol as dumpdevice