About this server

Some statistics, bandwidth graphs and Load graphs for all FTP machines.

Overview

This server is a cluster of three kinds of machines:
Backends
Reliable large storage that is NFS-mounted to all the frontends and offloaders, NAS-style.
Frontends
The machines behind the DNS names, handles ftp, rsync and most http requests, but passes http requests for large files on to offloaders.
Offloaders
Serves http requests for large files, distribution cd/dvd-images, movies etc.

Disk Backends

The current disk backend is a HP DL180 G6 server called brokdorf.

Total usable space is about 120TiB.

Frontends

We are using caching frontends to be able to deliver high bandwidth without having to have a disk backend that can handle the aggregated output. The cache used is mod_cache_disk_largefile, our modified version of the mod_cache_disk (previously mod_disk_cache) available in Apache HTTP Server. An XFS filesystem over striped SAS 10k/15kRPM disks is used as local storage.

For certain file endings (like .iso) we use http redirects to send these off to one of the offloaders. The choice of which offloader to redirect to is done by a perl program and is cached in apache as a dbm-cached rewrite rule. To keep cache size reasonably low a certain URL is always redirected to the same offloader.

The visible frontends are:

Offloaders

The offloaders work just as the frontends caching data locally, but they only handle a few large files. The majority of data is usually sent by the offloaders and cache re-use is high.

As a precaution against nosey users, the offloaders redirect directory indexes back to the main frontends. And as a precaution against stupid download agents we limit the max connections per IP to 10, and we always deliver data from cache if the data is cached, even if the user agent sends "Cache-control: no cache" or similar.

The current offloaders are:

Network

All machines are connected with gigabit ethernet, aggregated external bandwidth available is 6 gigabit/s.

Current and historical bandwidth graphs for the frontends.

Names

The server is known by many names. Among them:

Contact

If you have any questions please contact ftp-adm@acc.umu.se, and we will do our best to help you.

More information

Previous setups