Can I Mirror A Dump Area?

[A. Clay Stephenson · Accepted solution]

You can but it will not do what you expect in a system dump. If primary swap is also the dump area then it makes senses to mirror it (so that swap works with a failed disk) but otherwise not. I think dump will use the first volume displayed in the vgdisplay -v command as the dump device.

[Manju Kampli]

its not required to mirror the dump. The dump is used when there is a system crash. lets say you have system disk mirrored on to other disk.
configure the first disk LV (say lvol8) as dump and configure the second disk lvol8 as secondary swap.. so when the first disk fails, the system boots from the second disks and uses its local lvol8 as dump.. here since the other disk is not there, the socendary swap won't be there .. but no worries, your system will still work. When you have two disks, you have a luxary of extra swap ..

I have tried this and works OK.

hope this helps,
Manju

[Bill McNAMARA_1]

Mirror your swap which is possibly the same as dump in either case, but there is no need.

When a system panics due to some HPMC and ends up dumping the system will reboot.
On the reboot the dump space will be relocated to /var/adm/crash via the savecore rc script.

You can decide to dumpon a different disk, raid system if you really like.

[Magdi KAMAL]

Hi Fred,

The goal of mirror is to have a copy of data on another disk to prevent save data against failure ( hardware or software failure ).

In case of disk problem, you still have one copy on the other disk. So when you boot again you still have one data copy to continue work with.

But the swap is used to save process context ( program code, registers, stacks, ... ) when these process looks for resources which can not be satisfied immediately, the scheduler put such process into swap till these resources will be available.
When the system crashes, the content of memory, swap and other diagnostic are written to /var/adm/crash to save the situation allowing the debuging of the crash reason.

When booting the content of swap is an image of the new boot actual situation and haven't no relationship with the old one ( since it's in /var/adm/crash ).

I would recommand additing secondary swap instead of mirroring swap.

Magdi