Why use a check point file? was: Re: [RC5] client versions - AIX

Bruce Wilson bwilson at distributed.net
Thu Oct 3 10:33:33 EDT 2002

| Check point files are great for a machine with a harddrive.  
| I have machines that are nothing but a motherboard w/ a 
| network boot rom.  
| They have enough memory to load a distro, a ram drive and 
| dnet.  By using 
| battery backup and smallest block sizes (think: check point 
| file == micro 
| blocks), my network cranks and the power use is low... no 
| drives spinning, 
| or monitor glowing.  And no overhead of cluster software... 
| each machine is 
| quiet little node, doing a single job.  
| Yes, I had some nodes checking in work even 6 minutes, but 
| that is same 
| as a check point file, spinning up a hard drive, and writing 
| data.  But you see 
| I have one machine having to do that, the proxy server, and 
| since multiple 
| machines are crunching - the drive does not spin down.  
| Now you say... use a network drive to write that check point 
| file... Why?  It is 
| faster to return and request a new block from proxy, and I do 
| not have 
| support NFS mounts or SMB or worry about two machines sharing 
| the same 
| drive space.
| To add a new machine, setup the rom, add to bootp/dhcp and 
| away it goes.
| jackb

But why do you need to check in so frequently at all?  Since these
machines are single task, they must surely be quite stable.  The only
reason to check in partial work (or the smaller workunits you want)
would be to prevent the loss of work from a crash.  The machines you
describe sound like perfect candidates for "buffer in ram" with an
in-buffer size of 1 (or maybe 2).

I challenge you to find any other distributed project which gives you as
much control over your workflow as we do.

Bruce Wilson <bwilson at distributed.net>
PGP KeyID: 5430B995, http://www.toomuchblue.com/ 

Build a man a fire and he'll be warm for a day.
Set a man on fire, he'll be warm for the rest of his life.

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