> I think Jeff's problem is to have both data and filesystem integrity even if > the system experience a powerloss. > > ....Jeff, may you give us some more specifics?
Sure, I'll give you some more details in hopes that someone does my job for me. :) The constraints I am working under are: * Devices will be installed where maintenance is very expensive/difficult. They will be solar-powered, and with intermittent and low bandwidth uplink. A three year lifetime without repair is absolutely required, a five year lifespan would be better. * Devices will be running applications that were not originally designed for the embedded/remote/low-power/low-bandwidth setting. I seek to minimize the changes to the apps. * The applications demand things like Java servlets, SQL databases, Ruby on Rails, and all the rest of the heavy-weight software stacks found in Software As a Service settings. My current impression (not from measurement, but from look at best practice in the low-power device industry) is that I MUST NOT have a SQL server use a CF disk as backing store for routine transactions. I think it is certain the write transaction rate the CF disk will see would be incompatible with constraint #1. My current idea is that MySQL's data directory will be in ramfs, and that I'll have to build in hooks to the app to schedule a sync to non-volatile storage when required. But that means my databases can never be larger than RAM, which is a bummer. What I'd really like is a database config where the underlying tables are readable from non-volatile storage, but the application of transaction logs onto those tables was controllable, so that I can batch the updates (and remount RW only during the update application). It has long occurred to me that I should be recruiting colleagues not from the web-development community, but from JPL (where NASA makes space probes). Their environment is much more like my target environment. :) -jeff _______________________________________________ Voyage-linux mailing list [email protected] http://list.voyage.hk/mailman/listinfo/voyage-linux
