What are the highest-performance drive options?
Solid State Drives (SSD) have the fastest speed, lowest noise, and lowest data corruption. This is because there are no motors or moving parts to cause electrical and mechanical noise like in a Hard Disk Drive (HDD). HDDs are also know as a Repulsive Mechanical Device (RMD)...personally I find they sound repulsive in a high-performance music server.
Audio Video Drives (AVD) are a specialized variety of the HDD and have the next best-performance. The reason an AVD performs so well in a music server is because they are engineered for continuous play never pausing for read/write head self-calibration. An AVD will give consistently smoother playback than a standard HDD and is almost as good as an SSD. We consider AVDs to be the best value for use in a NAS/RAID array used for music library storage.
Hard Disk Drives (HDD) may have faster specifications than an AVD, but don't let that fool you. Those ultra-fast HDDs sold for network storage are engineered to have multiple users accessing data from multiple folders simultaneously. Unless you're building a file server for an online streaming service that kind of speed is totally ridiculous for music libraries. The problem with any normal type of HDD is that every 10 minutes or so they do a self-calibration of the read/write heads which manifests in a "blurb" in the audio. This is why professional recording studios only use AVDs in their servers and storage arrays.
External drive performance does not only come from the type of drive you use. The power supply, data buss, drive controller, case, data cable, and anti-resonant devices all make significant contributions to external drive performance.
What about Network Attached Storage (NAS)?
There is no performance advantage connecting a music server to NAS through an Ethernet cable. The only advantages of a NAS/RAID array are increased storage capacity, automatic back up (RAID), and multi-user convenience. A large SSD built into your music server has the best performance for your music library. Of course for optimal performance any internal storage drive should be isolated with a dedicated power supply.On the other hand, there is a significant performance advantage using a self-powered NAS/RAID arry that connects through an Ethernet port. This is because Ethernet has no buss power like USB, Firewire, eSATA, or Thunderbolt ports. Note that Ethernet peripherals are not plug-and-play like USB, Firewire, and Thunderbolt, and require a good bit of technical expertise to configure.
Are there any advantages when using Wi-Fi enabled NAS/RAID array?
The Wi-Fi from the router used to connect your NAS/RAID array can be used to control your music server. This allows you to turn off and/or remove all the noisy internal wireless control interfaces, such as WiFi, Bluetooth, and infrared, and to control your media server “headless” with a mobile device, such as an iPad.
You can connect a NAS/RAID arry directly to an Ethernet port on your internet service provider's (ISP) modem. This allows you to both stream music from an internet streaming service and to play music from your NAS/RAID array through one Ethernet port on your music server/streamer. And if your Internet Service Provider's (ISP) modem has WiFi this would allow you to turn off and/or remove your music server's internal WiFi lowering your noise floor and improving server performance.
What is the highest-performance type of plug-and-play external storage drive?
Thunderbolt, eSATA, and USB 3 drives have among the highest data transfer rates of any plug-and-play external drives. The drawbacks are that the controllers and cables are complex and there are few choices in a powerless audiophile data cable.
In comparison, Firewire and USB 2 controllers and cables are far less complex and many audiophile Firewire and USB 2 cables are available without power. Powerless data cables significantly reduces bit read errors and are highly recommended.
Before switching to a powerless data cable to interface with an external drive or DAC you need to make certain they don't require buss power. Some audiophile data cables have two cables, one for data and one for buss power. This type of cable would allow you to test components to learn if they require buss power.
Though technically slower than Thunderbolt, eSATA, and USB 3 drives, a high-quality Firewire drive that has a dedicated power supply and a powerless data cable is considered by many recording engineers to perform better. Of course fewer and fewer computers today still come with Firewire ports.