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I recently read about a company which setup all of their linux webservers to run without hard drives. This sounded really exciting to me because that would essentially mean that the biggest point of failure (HDD) is now gone. Furtheremore, when updating the OS (or anything else) for 5 or 10 web servers would be as easy as simply editing one image.

The million dollar question is, how is this done? what is needed to make this work properly and what are the PROS/CONS? It's a great sounding idea, I just hope I am not missing some really big issues.


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up vote 4 down vote accepted

PXE and a big ramdisk.

The good thing is that bringing up a new web server is as easy as turning it on. The bad things are that setting it up in heterogeneous environments can hard, and that each server can take a while to start up.

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And a decent SAN with preferably 10G Network backbone. And why not throw in some tiered storage on that SAN for good measure :-) – dunxd Oct 19 '10 at 20:09
@dunxd: Those are "added bonus features". They aren't required per se if all you want are "diskless machines". – Ignacio Vazquez-Abrams Oct 19 '10 at 20:13
@dunxd: i've done that for a distributed storage system, (think mogileFS, but done a decade ago). the 100Mbit ethernet used for PXE was far more than enough. once the image is loaded, it's all on RAM – Javier Oct 19 '10 at 20:28
Regarding image size, I would most likely use FreeBSD for the web servers so I think I can make the actual image pretty darn small. I am doing more research to find out if this is a good idea for a small scale (3-4 web servers) website. – dingalingchickenwiing Oct 20 '10 at 0:30

As well as Ignacio's PXE option you can also boot from iSCSI or FC/FCoE which will allow you to distribute your boot points if required so as not to overload a single server.

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Boot load distribution can also be done with PXE via configuring the DHCP server to use different TFTP servers, but it may still be possible to overload the medium. – Ignacio Vazquez-Abrams Oct 19 '10 at 20:30

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