Hi

I have "merged" Fedora Core 1 and Ubuntu onto one drive.

Fedora was originally on hda and Ubuntu on a drive in another identical PC. I managed to copy the Ubuntu image onto hda, then thought I'd be really clever and use the spare drive to create a universal /home.

In this way both distros can access the same /home. This works fine.

BUT, Ubuntu seemed to use more space for swap. Now on my hda is the original fedora swap of about 126M, whereas Ubuntu's was about 600M

Ubuntu is running slowly, so I have repartitioned hdb and put an 800M swap file on there. I then changed fstab to say:

/dev/hdb3 none swap sw 0 0

But it won't use it. A df -h shows /dev/shm as only the 126M partition.

The partition is correct and is of the right type. I am now wondering whether swap HAS to be on the first drive?

What have I failed to do - or done wrong?

Thanks

run this

swapon /dev/hdbX

whatever ur swap partition is
and also run
swapoff /dev/hdaX
to stop use of this swap partition

regards

Thanks - perfect!

I now have 1.2G of swap. This may be too much, but if it doesn't slow it down, it will be ok.

I need to sort out in my head the difference between tmpfs and swapfile.

Thanks again.

Tmpfs is a filesystem that is stored in ram. Conversely, swap is a way for "virtual ram" to be stored on disk.

FYI, Look into the pri= option of fstab for multiple swap spaces: with swaps on multiple drives, you can see a significant performance boost if they are at the same priority. Otherwise (as a default), the first swap must be full before it uses the second.

gr8

well if i have good amount of RAM then i do not like to use more swap
it can slow down some time too

It's a good idea to have swap-space on multiple drives, particularly if your hardware is such that more than one input/output operation can be going on simultaneously.

The rule of thumb, afaik, is that total swap-space should be about 2x the size of RAM. Beyond that, it probably won't be used. And of course, "chips are cheap." Purchase as much RAM as the box will hold.

lots of swap doesn't slow things down
swap on two different hardrives is a good thing

having no swap and lots of ram is worse than having lots of swap and lots of ram just because the kernel vm is designed to have swap -- without swap the kernel vm is all screwed up

well i meant to say that ,it is not good to be much dependent on swap

if i have good RAM then i like to minimize swap usage with modifying some kernel VM parameters

regards

Thanks for that - it has helped greatly. Made it a lot clearer!

It certainly is running quicker now I have it enabled. It crashed earlier when I was scanning a large image. Now it's fine.

Thanks to all of you!