Livecd vs. hard disk

Message

george · Post by **george** » Thu Nov 06, 2003 11:35 am

I have an application which would benefit from being run without a hard disk. I have been reading lots of stuff about using a livecd (based on either gentoo's or knoppix) but I'm left with a few questions. Hopefully someone will have used a cd based setup and can answer me

How does the performance compare between running from CD and from hard disk?

Are the memory requirements different? I realise that various files need to be mounted on a tmpfs which will use ram, and that I would have to run without swap. I haven't worked out if initrd and/or cloop need to be completely loaded into ram.

Is it possible to take the cd out to access data on another one?

If this does look worth spending the time on then I am leaning towards starting with the gentoo livecd because, if I can get working at all, it will be easy to choose what goes on it.

To save some possible posts, I have spotted fb-livecd and I would put /home on a usb memory stick.

TIA for any info.

Unik · Post by **Unik** » Thu Nov 06, 2003 1:47 pm

I had little experience with liveCDs, but already had some negative effects. First of all, the load time for applications is (obviously) much slower. Memory usage depends of whether you a going to launch some server apps like Apache, which will eat your memory (provided that you have /tmp and in tmpfs filesystem) like a hungry dog. Personally, I came up to using liveCDs only for recovery and management tasks.

george · Post by **george** » Fri Nov 07, 2003 9:15 am

Thanks Unik. I was thinking of workstation apps rather than server.

db_404 · Post by **db_404** » Fri Nov 07, 2003 4:38 pm

I built custom live CD for use as a firewall, and I've been very pleased with it . Saves on one HD and I can easilly switch machines in the event of a hardware problem.

Things to consider:

1. As everything is in RAM you have to take care that no application is writing incremental data to your ramdisk (you pretty much have to have some ramdisk available as you need it for things like wtmp and lastlog). In my case doing things like remote logging helps.

2. As already mentioned load times are slower - which may or may not be an issue depending on your application. For a firewall, it's not.

3. To persist data you will either need some networked storage (NFS, SMB or the like), or allow some access to a local storage device (I believe knoppix can save settings to a local device).

I don't think you'll be able to remove the CD while you have any file systems mounted off it, at least I've not been able to work out a way of doing it short of having everything in ram (which isn't really practical for a 32MB firewall....).

BTW I based my system off Slackware Live CD http://www.slackware-live.org/ as it looked a little easier to get into than knoppix.

george · Post by **george** » Tue Nov 11, 2003 9:26 am

Thanks db_404, this has had to go the back burner for now.