Re: [gentoo-user] nfs over (lvm over nbd) ?

[Philipp Riegger]

On Wed, 2009-05-13 at 01:58 +0200, Raph wrote:
> There are 20 computers (2x1.6 Ghz, 1GB RAM, 160GB sata)
> and 1 more (outside the room) with the same hardware
> (so no real "server"). The whole is connected
> with 10/100 ethernet.

This sounds quite ok. The question is, what will you use the systems
for? Because if you do no video, sound or picture editing on a larger
scale, not movie or music sharing, then you don't need that much
storage.

> - Each client (one of the 20 computers) runs a MBD daemon
> which shares its HD to the server (the 21st) over the
> ethernet.
> - The "server" handle the 3.2TB in a volume group and
> create the logical volumes with LVM
> - The "server" also run a NFS daemon
> - Then each client can grab it's data through NFS.
> - happiness ... ?

I'd say no. The setup sounds very very complicated and error-prone.
Before doing this I'd get rid of 1-3 Workstations and put those 1-3
harddisks in the Server to have more storage.

> - each client need some private HD space to, at least,
> boot enough to let the NBD daemon start.

A Gentoo installation is usually between 10 and 20 GB for me, I think.
You can also boot over ethernet.

> - $10 question : if 20 users login, will the ethernet
> be fast enough to support the load ?

Most liekly yes. Maybe it's a little slower, but it will work.


Here is what I'd do:

1) Make normal Gentoo installations on the Workstations. You can most
likely install 1 machine, put the image on the server and copy it
everywhere from there. IP and hostname can be managed by DHCP.

2) Use a NFS shared directory for portage tree and binpackages (for
updating, installing new software).

3) Install the Server. I would recommend using a softraid and therefore
taking the disk from 1-3 Workstations. Then you have 160-320 GB disk
space (RAID1 with 2, RAID5 with 3, RAID6 with 4 disks). For a Server 10
GB for / are enough, make it a little bigger, add some space for the
portage tree and the binpackages, and you have 120-280 GB for /home,
which is really a lot.

This shoulc all be a quite stable setup. Now, if you really need much
more disk space, you can do the nbd/nfs approach (or do it completely
distributed with a Cluster Filesystem and Cluster LVM, but that might be
more work).

Often people need some local disk space and only need it for 1
"session", therefore mount a big partition somewhere (/tmp maybe) and
run tmpwatch regularly. Maybe create a script that automatically
creates /tmp/home/$user for all available accounts. Maybe symlink it
to /home/$user/tmp or something.

Philipp