Re: postgres on a PDA

In article <1883.1042606899@sss.pgh.pa.us>,
Tom Lane  <tgl@sss.pgh.pa.us> wrote:
>attention I think it was on the order of magnitude of 10000 write
>cycles --- which Postgres could blow through in no time.  I hope
>it's better now, but I dunno by how much.  Anyone have more
>up-to-date info?

Only about 1 order of magnitude better.  From the Linux Embedded FAQ:

3.3 Flash Limited write cycles

   Flash  have limited write cycles capabilities from 200 000 to 400 000.
   Using  swap  on such device is dangerous. 300 000 writes gives you 200
   days  at  1  write / minute and 83 hours at 1 write / second. More, If
   you interrupt power at arbitrary times while the device is writing,
   you can lose the integrity of the file system being modified. The loss
   is not limited to the 512 byte sector being modified, as it generally
   is  with rotating disks; you can lose an entire erase block, maybe 64K
   at once. The risk goes up as the "disk" approaches full, because erase
   rewrite  cycles happen more often in this condition. Un*x file systems
   spread their super block tables around the "disk", in the hope that at
   least  one will survive a head crash. Create one file, then /bin/sync:
   what percentage of the device's erase blocks get hit?


I like the part that goes "you can lose the integrity of the file system
being modified."

To be honest, would BerkeleyDB be better?

mrc

--
     Mike Castle      dalgoda@ix.netcom.com      www.netcom.com/~dalgoda/
    We are all of us living in the shadow of Manhattan.  -- Watchmen
fatal ("You are in a maze of twisty compiler features, all different"); -- gcc