recommendations for a NAS drive

1. Almost any NAS works with Sonos, look for SMB sharing

2. All Sonos share a NAS.

3. Your phone is just a remote control, the Sonos play the music from your NAS.

4. The 0 tb is how much storage it comes with (NONE) and 36 to is the maximum size drives you can add. 1 tb is likely more storage than your music will need.

Several good NAS topics here, search on NAS and you will see what others have done.

1. Are you using S1 or S2 on your Sonos? S1 requires SMB v1 (a method by which Sonos connects to the NAS, which is now deprecated by most NAS makers, and harder to turn ‘on’, if even possible), S2 requires SMB v2 or higher, which are more secure methods for the Sonos to communicate with the NAS.
2. Yes.
3. Your phone could remain the controller.
4. Depends on what drives you’ve inserted in it, and how they’re set up. Contact Synology for more assistance. And each ‘song’ can be wildly different in size, so defining ‘how many’ really isn’t helpful. If the drives are larger than a gig each, it’s unlikely you’d run out of storage space, even depending on how they’re formatted. 

Thankyou, Stanley_4 and airgetlam. That was very useful. 
re: your questions - I have about 1TB of music files currently stored on a Dell tower pc. 
I am using Sonos 2 - to play songs I have stored on my iPhone. 

If I have understood correctly, the NAS Synology DS223J will be compatible with the Sonos amp I have in my kitchen (and any future Sonos amps bought for the lounge) but because the NAS comes with no storage, I would need to buy a drive too (I’m looking at a bundle that would include an installed Synology HAT3300) for a total cost of £380.  
Couple of follow-up questions, I’d appreciate your help with:

1 Is it possible to connect my Dell tower pc (which currently stores the music files) to the NAS and not buy the Synology drive. Although, I guess if this was possible I would need the pc running all the time to play any music? And it would by good to free up space on my pc. 

2 Am I right in thinking that Sonos is limited to recognising 65,000 songs? If I have more than 65000 songs on the NAS drive, will that affect my  capability to play the songs I have stored in any way? 
Thanks again for your help with this, both of you. I will contact Synology as suggested but all your advice on the Sonos side is very helpful, especially as I am very new to all of this. Much appreciated. 

I took Synology off my shopping list when they added a requirement to only use certified drives, expensive ones. So I can't answer much about them directly. Make sure you get drives that will work, the kit option is good.

The NAS shares internal drives by default you might rig something ugly up to get it to share external drives but then why have the NAS in the first place, it would not add anything good, just a couple extra points of failure.

The number limit is the most Sonos can find. There is also a soft limit on meta-data that is rarely encountered. Calling Sonos support after sending a diagnostic can get you status information on both limits.

1. Doesn’t make any sense, the Synology is the NAS. Yes, your laptop/desktop will be connected to the Synology. If the music is stored on the NAS, then no need to have your PC running. The Sonos will reach out across the network to the running NAS and grab that music. 
    
2. Yes, there’s a (rough estimate) of 65,000. But it’s based on memory for the song, and the associated ‘tags’. You might get slightly more, or slightly less. Sonos does work with Plex, which overcomes this limitation. I’ve not installed Plex, as my library is smaller than 65,000 pieces. You may want to look at Plex, if your library is that huge. I suspect Plex has an FAQ, perhaps more comprehensive than the Sonos FAQ, which I’ve not read. You may also want to search these forums for mentions of ‘Plex’. 

I want to use my Sonos system to play music from my full library stored on a NAS. From what I understand, a Synology DS223J will work with my Sonos amps in the kitchen and any future ones in the lounge. I would need to buy drives for it since it comes with none.

If the music is on the NAS, I don’t need my PC running all the time. I also understand Sonos can handle around 65,000 songs, and using Plex could help if I go over that.

Thanks for the advice so far.

hi ​@Tuckor Morine and ​@Si1verback , I am successfully using Synology NAS for my iTunes library for many years now and wrote a few recommendations on my blog how to keep the library updated for SONOS - my music library holds over 25k tracks using 188GB disk space

hope this helps