Running from Ram

[lazlow]

Hey Guys

With the price of ram so cheap I had a thought. When I first tried F8_64bit I ran the liveCD in the run from ram mode and it really screamed. Now for my regular desktop 2gb of ram is about right, but what if I bumped up to 4gb of ram and ran the system from ram all the time? What would be the "issues"? How tough would it be to set this up?

Just a thought.

Lazlow

[kona0197]

You would lose all your custom settings should you power down...

[Nokia]

He said running the OS, not keeping his data in a ramdisk In other words, data should stay on the HDD as usual.

[kona0197]

Well what if wants the OS to show the fonts different for example? He would lose that setting everytime he shut down.

[lazlow]

Kona

I am not sure about where those type files are stored when running from ram, but even if it was in ram you should be able to update all that type of information back onto the hard drive (where you booted from) using a shutdown script.

Considering that I pretty much only reboot my machines to install a new kernel (I think a lot of us do this), the time needed to do this would be minimal.

[stevea]

You can't run a ram based file system and then expect your configs to generally be saved. There are some good (and probably better) options tho'. A compromise would be to put /lib, /usr/lib /bin, /usr/bin on ramdisk - but you'll have slow startup time and you'll miss a lot of executables.

Look at the prelink and preload packages. The do just about the ideal thing for performance when properly configured. Also the cache/swap scheme already does just about an ideal job IMO.

There is a new-ish 'xip' (execute in place) capability in some of the file systems that I haven't explored, but if you really had a need for a ram file system for execution speed you'd definitely want xip. [[It's really targetted at flash based embedded systems]]..

[lazlow]

Stevea

I think you were typing as I posted (#5).


I took a look and the directories you listed would be well under 1GB in total (on my system).


I guess I am unclear on the "you'll miss a lot of executables." section. I assume the slow startup time would be copying everything into ram. An extended boot up once every two weeks would not be much of an issue for me.

For the most part I do not use swap at all, except when I run one custom app. I know when I am using swap and I am not thinking about boosting performance at those times. So I think the cache/swap thing is really a non issue(in this instance).

I guess I am still just shocked at the speed difference between running the livecd in ram mode and running off the HD. The HD are fine, roughly 75MB/sec from hdparm -tT.

Edit:

http://en.wikipedia.org/wiki/Comparison_of_file_systems

Above says that EXT3 supports XIP(if I am reading it correctly).

[kona0197]

Lazlow I turn my PC off every night so I guess I'm the exception.

[NoWayBill]

DSL has a backup to hard drive feature, but we're talking about Fedora.

Google create live linux cd returned this http://www.linux-live.org/ as the first hit.
Looks very interesting, might have to try it myself.

After reading the site....
I'd suggest using Kickstart to create a custom Fedora build with only the apps/services you desire to keep it lean and trim.
Burn, install, and tweak it, then create a LiveCD from that install.

Man-oh-man, lazlow, I think you've set me on a mission.

[lazlow]

Bill

I want to do this with a full install of Fedora. I do not want to run it from a CD.

[kona0197]

Run it from a hard drive then...

[savage]

I reckon this can be done, and would be lightning fast too, I am guessing though.

At the very least, you would need /etc and /home mounted to hard disks, and possibly /var too, that will keep your user and app settings.

The main problem, is installing additional software once your setup, as you would need to update the image that goes into RAM each time, otherwise any OS changes will be lost when you power down. Unless you devise some way to save the image on shut down, this will add time to the shutdown process.

Also, keep in mind that this would limit your root partition to 2GB too, I don't think you could squeeze a huge amount of software in that.

Boot times will probably be increased a lot, since that 2GB image will initially need to be copied from somewhere, probably a hard disk?

I'd be interested to know if you manage to pull it off.

Savage

[techmatt]

I think it could be done rather well

on startup
create ram disk
copy files to ram disk

on shutdown
copy ram disk to hd

sounds simple but would increase startup and shutdown times

[Nokia]

Since it hasn't been suggested so far, you should consider a reliable UPS in the first place.

[techmatt]

well might not be needed so much if you simply set it up to copy back to hd every once in a while.
I would probably use rsync to update the hd every hour or two.