Juan Céspedes - Plan 9 

To set up a venti server, you can read the manual pages, or follow these simple rules. You need, at least, three things:

1. A configuration file (usually called venti.conf)
2. one arena partition
3. one index section

The configuration file is a text file which tells the server where to find the rest of the files, how much memory to use, where to listen for client requests... This file consits of lines with two words each: a reserved word, and a parameter. The simplest configuration file is:

index main
arenas /path/to/arenas
isect /path/to/index

The config file can have more lines:

• There can be more than one arena partition (more arenas lines)
• There can be more than one index section (more isect lines)
• bloom /path/to/bloom

  Bloom filter, optional file that is stored on disk but also kept completely in memory while the venti server runs. It helps the venti server efficiently detect scores that are not already stored in the index.

• mem size

  lump cache sizelumps, which holds recently-accessed venti data blocks. The default value is 1MB.

• bcmem size

  block cache size

• icmem size

  index cache size

• addr netaddr

  Network address to announce venti service (default tcp!*!venti)

• httpaddr netaddr

  Network address to announce HTTP service

All the sizes are specified in bytes, and the amount can be appended by a k, m o g to indicate kilobytes, megabytes or gigabytes.

The file names can be expressed as file:lo-hi to specify a range of bytes within the file. Either lo or hi may be omitted, to indicate the beginning and the end of the file, respectively.

The arena partition (/path/to/arenas) holds, in sequential order, the contents of every block written to the server. It is logically split into sections called arenas, each of one has 500MB.

The index section (/path/to/index) helps locate a block in the arena partitions given its score. The suggested index size is 5% of the arena partition.

In order to start the server, you must format the arena partition and the index section first; then, you have to format the main index:

venfi-fmtisect isect0. /path/to/index
venti-fmtarenas arenas0. /path/to/arenas
venti-fmtindex venti.conf

And that's all! You can now start the venti server by running venti.

For those of you that still don't know venti, I will say that it is a network storage system, heavily used in Plan 9 from Bell Labs and, thanks to Russ Cox, it is part of plan9port (Plan 9 from User Space), and hence it can be used in other operating systems.

Venti is a block storage server intended for archival data. In a Venti server, the SHA1 hash of a block’s contents acts as the block identifier for read and write operations. This approach enforces a write-once policy, preventing accidental or malicious destruction of data. In addition, duplicate copies of a block are coalesced, reducing the consumption of storage and simplifying the implementation of clients.

Venti is the system I use for back-ups of all our Linux machines at work; it is very easy to use, very efficient and very useful. The only problems I see is that it is not yet packaged in Debian, and its compilation and installation is not very straightforward; that is why I packaged it for Debian, creating 2 packages:

• venti-server: It includes the server (venti) and some utilities to create and configure it.
• venti-client: Some clients that talk to a venti server, such as vbackup, vac and vnfs.

I packaged version 20100416-1, but it is not published anywhere yet (but drop me a note if you would like to get it).