I'm thinking about setting up a software raid level 5. Is it possible to start with 3 HDs and then later add more? I mean, without loosing the data on the first 3 HDs.
Yes, on most *good* hardware RAID cards and also (I think) on Linux software RAID.
What you do is add a disk, then use the RAID tools to add the disk to the array. You now have a larger array, with some wasted space because the filesystem (/usr, for example) did not get expanded. Finally you use a tool like GNU parted (included in Fedora) to resize the filesystem.
However, you're using RAID 5 to prevent data loss. And although I've used parted for years without a single problem, you should never mess with filesystems or other critical schema without first backing up all your data. But since your RAID 5 may just be too big to easily back up, most people then proceed to resize the filesystem without a backup. And probably 1 in 1,000,000 people is going to lose data.
As the man said, "you pays your money and you takes your chances."
-- Rodolfo J. Paiz rpaiz@xxxxxxxxxxxxxx http://www.simpaticus.com
