Hi Jeff,
Running mysql server under harsh and embedded environment is a wrong
design decision IMO. At least you should consider using sqlite to
replace mysql. It is easier if your application is running java, where
switch jdbc driver is straightforward. Hence, you can keep sqlite files
in ramdisk and do a sync to disk every day or several times a day.
Regards,
Punky
Jeff R. Allen wrote:
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
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--
Regards,
Punky
Voyage Solutions (http://solution.voyage.hk)
* Embedded Solutions and Systems
- Mesh Networking, Captive Portal, IP Surveillance, VoIP/PBX
- Network Engineering, Development Platform and Consultation
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