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> So now you can ask some hard questions: what if the power goes out > completely or the host crashes or something else goes wrong while > critical data is still in the ramdisk? Easy: use reliable components. Nice fiction - stuff crashes eventually - not that this isn't useful. For a long time simply loading a 2-3GB Ramdisk off hard disk has been a good way to build things like compile engines where loss of state is not bad. > If UPS power runs out while ramback still holds unflushed dirty data > then things get ugly. Hopefully a fsck -f will be able to pull > something useful out of the mess. (This is where you might want to be > running Ext3.) The name of the game is to install sufficient UPS power > to get your dirty ramdisk data onto stable storage this time, every > time. Ext3 is only going to help you if the ramdisk writeback respects barriers and ordering rules ? > * Previously saved data must be reloaded into the ramdisk on startup. /bin/cp from initrd > * Cannot transfer directly between ramdisk and backing store, so must > first transfer into memory then relaunch to destination. Why not - providing you clear the dirty bit before the write and you check it again after ? And on the disk size as you are going to have to suck all the content back in presumably a log structure is not a big concern ? > * Per chunk locking is not feasible for a terabyte scale ramdisk. And we care 8) ? > * Handle chunk size other than PAGE_SIZE. If you are prepared to go bigger than the fs chunk size so lose the ordering guarantees your chunk size really ought to be *big* IMHO Alan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | |||||||||
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