The idea of a RAM disk based database and reliable storage are in
complete opposition. Forget it.
The question is: What do you need the *raw* speed of a RAM disk for, and
what can you tollerate for overhead for reliability?
You have posed a question about how to implement a flawed solution, what
is the original problem you are intending to solve?
Chris Sutton wrote:
>Hello,
>
>I need some insight on the best way to use a RAM drive in a Postgresql
>installation. Here is our situation and current setup:
>
>Postgresql 7.2.1
>Dual PIII 800
>RAID 5 SCSI disks
>Platypus 8GB PCI QikDrive (the RAM drive). http://www.platypus.net
>
>The Platypus RAM drive is a PCI card with 8GB of ram onboard with an
>external power supply so if the main power to the server goes off, the RAM
>is still powered, so it's persistent between reboots.
>
>Currently the disk size of our database is 3.2GB, so we put the whole
>pgsql directory on the RAM drive. Current preformance is very
>snappy with the bottleneck being the CPUs.
>
>The concern of course is if something happends to the RAM drive we are
>S.O.L. and have to go to the last backup (pg_dump happens each night).
>
>The other concern is if the disk size of the database grows past or near
>8gb, we would either have to get a bigger RAM drive or somehow split
>things betten SCSI and RAM drive.
>
>I don't quite grasp the full inner workings of Postgresql, but
>for those of you who obviously do, is there a better way of setting things
>up where you could still use the RAM drive for portions of the pgsql
>directory structure while putting the rest on disk where it's safer?
>
>Should we just put pgsql/data/pg_xlog on the RAM drive?
>
>Also, in the very near future we will be upgrading to another server,
>pg7.3.2 with dual P4 2.4 xenon's. The RAM drive will go into this new
>server.
>
>Any suggestions?
>
>Thanks
>
>Chris
>
>
>
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