Messages in this thread |  | | Date | Thu, 4 Jan 2001 21:31:46 +0100 (CET) | From | egger@suse ... | Subject | Re: Journaling: Surviving or allowing unclean shutdown? |
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On 4 Jan, Richard B. Johnson wrote:
> A mobile-phone that runs out of battery power will also lose all the > phone numbers you have stored, etc. The same is true for most all > embedded systems that save data.
In your world maybe. I would be quite pissed if my mobile phones lost the stored numbers every time they run out of power. Nearly all embedded devices nowadays keep their settings without power; be it a satellite receiver, a PBX, a fax machine or a coffee brewer.
> This means that the data-base > software has to roll-back and redo the temporarily-lost updates > when it restarts. It uses the journal to accomplish this. As > N-seconds gets smaller, the overhead necessary to maintain data > consistency gets greater, so there are trade-offs.
And depending on the application they may really be worth it.
> A journaling file-system also needs some number to show the > order of operations so that roll-backs and restarts work. > Unfortunately, the systems that I have seen all use time for > the number! You don't want time to reconstruct 'order'. You > need a number that represents 'order'. Time is not your friend.
Since the metadata has to be sync anyway what about using a normal transaction counter?
--
Servus, Daniel
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