Date: Fri, 18 Nov 2005 23:39:59 +0100 From: Michal Mertl <mime@traveller.cz> To: Johan =?ISO-8859-1?Q?Str=F6m?= <johan@stromnet.org> Cc: pjd@freebsd.org, delphij@delphij.net, freebsd-stable@freebsd.org Subject: Re: Page fault, GEOM problem?? Message-ID: <1132353600.903.19.camel@genius1.i.cz> In-Reply-To: <A6F22EE2-B1E6-44B5-B4C2-E77E1A24FEBB@stromnet.org> References: <991F35AA-151B-4AEA-82BD-5F4AEDF28424@stromnet.org> <a78074950511180117r6d64db25o4ae37c0c5998e002@mail.gmail.com> <74994962-5050-47BD-897B-DE3880B9EBD5@stromnet.org> <a78074950511180943r57fd9d03r64efcc705001bc35@mail.gmail.com> <A6F22EE2-B1E6-44B5-B4C2-E77E1A24FEBB@stromnet.org>
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Johan Ström wrote: > Hi! > > On 18 nov 2005, at 18.43, Xin LI wrote: > > > Hi, Johan, < large snip> > So, it seems it does run savecore after running dumpon and mounting > disks etc... Is that wrong? No, this is normal. When you run savecore you need to have mounted filesystems. In order to mount the filesystems they may have to be checked. The fsck program requires big amount of memory to check larger filesystems so the swap has to be enabled. Core dumps are written to the dump device (swap) from the end whereas the swap is normally used from the beginning (or the other way around). Therefore there's quite a big chance that, even when the swap has to be used for fsck, the core dump is intact and usable. If the usage of the swap file by fsck corrupts the core dump you may start after next crash in single user mode and run the commands manually (without enabling swap). As to why you can write kernel core dumps only to certain devices the answer is that at the time, when the kernel is dumping core, it is usually in pretty bad state, kernel internals may be corrupted and so on. The dumping code is therefore written to be quite low level so that even wedged kernel can be dumped. The dumping code is part of hard disk controller's drivers. The gmirror is quite high-level device and geom itself needs working scheduler so there will probably never be a way to dump on gmirror provided swap. When you issue the dumpon command the check is performed whether the driver for the disk you want to dump on supports kernel core dumps. Michal
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