Unionfs for Linux?

Lukey Boy asks: "A machine in my network is currently a large fileserver, and holds many hard disks full of media (namely my music and what not). Each drive is running a standard EXT3 filesystem with the same layout (/media, /media/mp3, and so on). My problem and question is how do I join these drives to look like a single hierarchy? I would like to, when I check /all/mp3, view the contents of each drive in this combined directory. FreeBSD has a unionfs filesystem type which supports the unioning of two drives - but only two is a fairly bad limitation, especially when I add a new drive. It appears that Al Viro is working on a unionfs for Linux 2.5, with again only two mount points supported. I was also considering using the Linux Volume Manager system, or possibly a software RAID striping arrangement; does anyone have any experiences doing anything similiar? Is there any decent inheritable filesystem (IFS) available for Unix machines?"

Comments

why does it hurt when i do this...

[kevin lyda]

there's an old joke about a guy going to a doctor who complains that it hurts when he holds both his arms above his head and yodels. (or something like that) the punch line?

don't do that.

unionfs with two fs's really isn't all that great idea. and no offence, but unionfs with more then two fs's is monumentally stupid. where do new files get created? how do you deal with conflicts? what happens with files that you edit? what if you remove a file that exists on more then one fs?

there are a slew of different answers to these questions so either the kernel inflicts (and yes, i mean inflicts) policy or you have to provide a way to configure all those options. should mounting fs's get as complicated as firewall rules?

there are lots of solutions to your problem. pick one of them rather then a bigger problem.

Re:why does it hurt when i do this...

[adolf]

Witty. Constructive. +4.

I like it. Not.

If "there are lots of solutions" to the problem, showing at least one of them would perhaps turn outright discouragement into something useful.

The problems are obvious. And they have been solved for a long time - witness TVFS under OS/2. Does something similar exist for a free OS? LVM might be close.

Mounting filesystems should be no more nor less complicated than is needed to achieve the desired goal. If this means that it's "as complicated as firewall rules," so be it.

Seems that this is already the case, anyway. I've got three lines of firewall rules. The fstab on the same machine trounces that handily, without doing anything creative or silly - just mounting various partitions to various points.

(and before anyone asks how it can possibly be secure, I'll say this: It's -STABLE, and that's good enough for me.)