
Some may also be wondering what type of Network Attached Storage device (NAS) to purchase; if that is your chosen resolution. With the many NAS devices on the market there are plenty to choose from. The amount of information regarding their Pro’s and Con’s can be confusing.
Just FYI….A NAS device consists of a hard drive (HD) for storage just like a computer. Also, just like a computer the HD can fail which is why it’s always recommended to employ a backup scheme using an external USB drive.
Therefore, if you purchase a NAS device with a single HD then make sure an external USB drive can be attached for backup. Some NAS devices will require that you manually execute the backup and others have software that can be programed to execute it on a schedule (i.e. set it and forget it). Typically (IMO) the back-up device should be at least 1.5 times the capacity of the NAS.
There are also NAS devices that have two (2) or more bays that accommodate multiple HD’s. I’ll limit this discussion to the 2-bay configuration. The HD’s can be configured in several flavors known as Redundant Array of Independent Disks (RAID). I’ll speak to the most common for the intended use with Sonos being RAID 0 and RAID 1.
Raid 0 is a single capacity configuration combining both HD’s as one. In Raid 0 your data is more vulnerable to loss.
When configured in RAID 1 one of the HD’s serves as the main drive to which all information is stored. The other drive acts as a MIRROR of the main drive. If one fails the data is still available on the other. Your data is less vulnerable to loss in this configuration. Now, I’m paranoid so even with the built-in redundancy I have an external USB drive attached with a scheduled back-up scheme.
* All monetary figures mentioned below are USD.
With a NAS device that accommodates two or more drives the HD’s are typically sold as separate components. Although some include both HD’s; but IMO they are of less quality.
The NAS itself is called an “enclosure”. From a price standpoint a NAS enclosure can be had for less than $100; if you shop the sales. One thing to note is that those (sub $100) NAS enclosures typically adhere to what is called SATA II (Serial Advanced Technology Attachment) which means they operate at 3Gb/s transfer rate. So if you want more speed you’ll want a NAS enclosure that operates under SATA III standards or 6Gb/s.
You might also consider an HD that operates at 7200 rpm versus 5400 rpm or the very expensive SSD. NAS enclosures that accept SSD’s are very expensive and are typically found in professional applications. There are more benefits to a higher priced NAS enclosure; but are probably of no consequence to the average user. For more information on SATA series click the link:
https://kb.sandisk.com/app/answers/detail/a_id/8142/~/difference-between-sata-i%2C-sata-ii-and-sata-iii
NAS enclosures typically accept drives that are 1TB or greater. That said a fully configured sub $100 2-bay NAS device may be priced around $240; using 1Tb drives at $70 each.
Bottom-line…you can spend a little or a lot (upwards of $1000+) for NAS depending upon your needs and your pocketbook.

Cheers!
Removing the 'On this iPhone, iPad, or iPod Touch' feature
https://support.sonos.com/s/article/2922?language=en_US
Using a NAS drive with Sonos
https://support.sonos.com/s/article/78?language=en_US
Importing playlists from other apps like iTunes
https://support.sonos.com/s/article/153?language=en_US
Music library troubleshooting
https://support.sonos.com/s/article/2401?language=en_US
Adding and updating your music library
https://support.sonos.com/s/article/257?language=en_US
Sonos and Incompatible Hardware
https://support.sonos.com/s/article/41?language=en_US