Adrift at Sea —Dan’s blog on dankim.com

Tim Bray has an interesting article over at his blog, ongoing, concerning his possible migration from CDs to using a music server of some sort to store his large collection of music.

I’ve written him several times regarding the idea. What follows is a slightly more coherent version of what I’ve written Tim.

The Problem (summarized from Tim’s website)

To be able to store and manage roughly 1,000 CDs worth of music. Previous obstacles include cost of storage, as this amount of music might take 500 GB or so of storage; computers being physically too noisy; and difficulties in getting a clean digital-analog conversion for playback.

The Solution

Currently, drive storage has come down drastically in price. A PC-based server with a small terabyte RAID array can be built for less than $2,500. The Mac mini is an exceptionally quiet computer, which is not unreasonably priced. The most difficult obstacle is the digital-analog conversion, as computers tend to be electronically quite noisy.

Specifics

Store the music on a server with a RAID 5 disk array. The RAID 5 storage array provides some redundancy for the large datastore, while keeping costs relatively reasonable. To use non-redundant storage runs risks in terms of losing the digital music files and would incur additional costs in time or expense of re-encoding any music lost to a storage medium failure. Serial ATA (SATA) RAID controllers are now available, as are SATA hot-swappable drive cages, which support five 3.5″ x 1″ drives in the place of three stacked 5.25″ drive bays. The actual server could be a Windows XP or Windows 2000 box with a five-drive RAID 5 array. The five-drive array would provide 750 GB of live storage with a hot spare. By running iTunes on the server, you can share the entire music library to any locally-networked computer running iTunes. The music archive could also be shared as a network drive.

The controller for the music archive is iTunes running on a Mac mini, located next to the main stereo system. The Mac mini, can be used to encode new music and add it to the music archive, as well as create and manage playlists. iTunes is now available for both Windows and Mac platforms and is basically interoperable. iTunes can be used to share and control the entire music collection relatively easily. The choice of a Mac mini over a Windows machine is based on machine size and the amount of noise generated by the computer. The Mac mini should be equipped with an Airport Extreme card as well as Bluetooth. The Bluetooth will allow the use of a wireless keyboard and mouse, making for a much cleaner, less conspicuous installation. A Bluetooth-capable cell phone as a remote to control iTunes, via software like Salling Clicker.

To transport the music from the network server to the location of the stereo, use an 802.11g network and the Airport Express. Output the music from the Airport Express using the S/PDIF (Sony Phillips Digital InterFace) optical line. This creates a complete digital path to the stereo equipment. By utilizing a S/PDIF input on the amplifier, the digital-to-analog conversion is removed from the computer system and handled by the audio equipment. It is very likely that any equipment with an S/PDIF optical input will be designed to have a high-quality DAC circuit to handle the input and convert it to a usable format.

The Squeezebox could also be used to do the DAC and music distribution. It would also have the advantage of having a remote control and not requiring a computer running iTunes to operate. However, the combination of a Mac mini and the Airport Express gives the system more flexibility than using a Squeezebox.

The first major difference is that the Squeezebox is a special single-purpose computing device and does not allow the flexibility a Mac mini offers. The MM/AE combination allows the encoding and addition of new music to the archive from the stereo console. It could also allow streaming of more than just audio. The Mac mini can also be used to stream Tivo video content from a networked Tivo. The Tivo needs to be modified slightly to allow this, but it is a relatively easy modification that has been well tested.

The second major difference is the MM/AE combination could allow the streaming of different music streams to different rooms, at a lower cost than the Squeezebox. The MM/AE solution also allows any visitors with an iTunes-capable, WiFi-equipped notebook computers to stream their own music to any stereo connected to an AE.

The last major difference is cost in a multi-room setup. The Airport Express is roughly a third the cost of the Squeezebox. It is relatively compact and inconspicuous. It can support either analog or digital audio output, with the understanding that the analog output will be of lower quality than the digital output. It can be controlled by any computer running iTunes. Multiple Airport Expresses are less expensive than multiple Squeezeboxes. The Airport Express can also act as WDS node for the WiFi network, while functioning as a music source.

Any room with an iTunes capable computer and an Airport Express could have a discrete music stream from the music archive. Granted, this makes a couple of assumptions.

• That you would have an iTunes capable computer in the room.

• That you would have sufficient bandwidth on the WiFi network to handle multiple audio streams.

• That the large archive would have sufficient speed to stream to multiple Airport Expresses.

The first is not too far a reach… if you have a notebook or desktop that is on the wifi network you can use it as a controller. An office would probably have a networked computer in it. The addition of the Airport Express would allow a discrete music stream in that room. In other rooms, a laptop or notebook computer could be used whenever necessary.

The second can be managed by proper network design, and implementing QOS on the network. The QOS would actually be implemented in the central WiFi access point. The central WiFi access point would probably be fairly close to the computer room, where the drive array is. A well-designed 802.11g network should be capable of two or three streams with little impact on other network services.

The third would easily be solved by using a RAID 5 storage array. The idea of having a significant fraction of a terabyte of digital music on a non-redundant drive is close to insane, as a drive failure would force one to re-encode any music lost.

Two last points:

Although a notebook could be used to control the music at the main stereo console–a dedicated computer for use as a controller in that location would make more sense. The use of the Airport Express would allow any visiting guests with an iTunes-capable, WiFi-equipped notebook to stream their own music and playlists to a stereo system without altering the music archive for the household.

Technical note:

The S/PDIF is an industry audio standard for digital exchange o The S/PDIF port can accept a standard 1/8″ stereo headphone type connector, but also accepts the S/PDIF connector. The cable is also often called a TOSlink cable. The optical connector (miniplug) that fits in the Airport Express is on the left and the TOSLINK connector on the right.