Messages in this thread | | | Date | 02 Nov 2002 15:02:00 +0200 | From | (Kai Henningsen) | Subject | Re: [lkcd-devel] Re: What's left over. |
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yakker@aparity.com (Matt D. Robinson) wrote on 01.11.02 in <Pine.LNX.4.44.0211011205330.26575-100000@nakedeye.aparity.com>:
> On Fri, 1 Nov 2002, Linus Torvalds wrote:
> |>And if you get these things wrong, you're quite likely to stomp on your > |>disk. Hard. You may be tryign to write the swap partition, but if the > |>driver gets confused, you just overwrote all your important data. At which > |>point it doesn't matter if your filesystem is journaling or not, since you > |>just potentially overwrote it. > > We haven't seen this before, but it is always a possibility for any > dump scenario. That's why you some choose netdump instead. :)
*If* you want safe dumping to a partition, it seems wrong to me to try to figure that out after the crash.
Instead,
* configure the crash space with a user-mode app or possibly a kernel command line arg * Whenever repartitioning, check if the crash dump partition is affected, and if so, clear it until it is explicitely reconfigured * Save a good checksum (say, md5 or sha1) of the crash partition config, and only dump if that checksum checks out
You might want to checksum even more than that, of course :-)
But there's certainly a reason Netware liked to crash dump to a series of floppies - too bad those are much too small for today's machines. When floppy sizes stopped to be slightly larger than standard RAM sizes[*], the computing public lost big time, and we haven't recovered from that.
[*] Apple ][+: 48 KB RAM, 140 KB floppy. IBM PC: 640 KB RAM, 1.2 MB floppy. (Yes, I know there were other combinations as well.) Where's my approximately-1-GB floppy that everyone and their aunt have installed today? No, CD writers are *not* universal. And burn-once CDs aren't much like floppies.
Of course, the same problem exists with general backup technology - tape the size of modern disks is not really affordable anymore.
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