Like many other NASes, the NAS540's capabilities can be extended by the installation of packages. In the new OS, the packages are a little more difficult to locate because Apps aren't on the home screen. Instead, you'll find them buried under System Settings->Firmware/Packages->Package.
There are currently only 13 packages available. From the Package page, you can retrieve a list from the Internet, install/upgrade, uninstall/cancel installation, enable/disable and get package info. In the course of this review, I installed several packages including the Google Drive Client.
ZyXEL NAS540 Package Management
Media Server - The NAS540 includes a built-in DLNA media server. It uses a Twonky media server that can be managed via browser on port 9001 of your NAS. The image below shows the server successfully indexed 126 videos, 2331 tracks and 9040 photos.
ZyXEL NAS540 DLNA Twonky Server console
One nice feature is the server automatically watches for new media and updates the index on the fly by default. There's no need to set a scan interval unless you want to. I tested playing media content using several DLNA devices, including the WDTVLive I use for standard DLNA testing, as well as several DLNA apps on my iPad. As expected, I encountered no problems streaming video, audio or running slideshows on any of the platforms.
iTunes - like many NASes, the NAS540 has a built-in iTunes server. I enabled the server and tested it using iTunes on a Windows 10 system. iTunes found the server and was able to play the content back as expected.
GoogleDriveClient - This is a pretty useful application but not installed by default. During the configuration process, you specify a target volume \ folder on the NAS. Google will generate and display an authentication key that you enter into one of the final configuration screens.
Once configured, this application does a true two-way synchronization between the specified volume \ folder on the NAS and your Google drive account. File additions or deletions in either location are automatically synchronized. Testing found it worked exactly as expected. This could be a very handy feature if you already back up photos or other mobile data to Google Drive. I've set up a short gallery to show you the configuration process for Google Drive Client.
Dropbox - This application is not the equivalent of GoogleDriveClient for DropBox. When you log into your Dropbox account from the app for the first time, you have to grant permission to allow the NAS540 to access files and folders in Dropbox. Two directories are created in your Dropbox folder: Drop2NAS and zDownload.
Drop2NAS - According to the documentation, the NAS540 connects to Dropbox and copies files in the Drop2NAS to its admin\dropbox\FromDropbox. It then empties the Drop2NAS folder. This helps keep your DropBox cloud storage clean, and ensures that you have a copy on your NAS.
zDownload - here's what the documentation says about the zDownload folder:
The NAS540 copies *.torrent files in the zDownload folder to the NAS's admin\download\torrents folder and automatically starts downloading them. The NAS adds a suffix to the name of each torrent file in the Dropbox account's zDownload folder and keeps updating it to show the job's state. (downloading, queued, paused, canceled, uploading, finished, error, or retrying). The NAS does not take any action for folders nor other types of files in the zDownload folder.
Unfortunately, it doesn't look like you have the ability to change the default download directory.
Copy/Sync Button - This feature allows you to copy to/from a USB storage device and the NAS540. To activate this feature, you select a NAS copy Target on the NAS, specify the USB volume and choose the copy direction - either USB->NAS or NAS->USB. A short press and release of the Copy/Sync button on the front panel of the NAS540 starts the copy process.
If you press the button until you hear a beep, you start the synchronization process. You have similar synchronization options: USB->NAS or NAS->USB. In addition, you can sync NAS<->USB with the option of backup files to be replaced or removed. The screenshot below shows the Copy/Sync button configuration screen showing the drop down Sync Direction choices.
ZyXEL NAS540 Copy/Sync button configuration
I tested this feature and specified a USB->NAS copy of about 14 GB from a flash drive inserted into the front panel USB 3.0 slot. All files were copied into a new folder with a name using date and time format (2015-08-31_25_06_35).
ZyXEL zCloud Mobile Apps - Any NAS with "Personal Cloud" as part of its product name provides mobile apps so you can enjoy your media content from anywhere. Unlike some NAS manufacturers that have separate applications for video, audio, photos, file access, etc., ZyXEL has one app each for iOS and Android. You can download them at either the Google Play Store or the Apple App Store, or use one of the QR codes below.
ZyXEL zCloud QR Code for iOS and Android
Both the iOS and the Android apps have similar feature sets, letting you play photos, music and video and browse files. You can also download any of the multimedia content on your NAS, or you can upload photos from mobile device. The file browser shows all your available shares and you have normal move, copy, delete, and rename options. You can also download or share files.
While both apps have similar features, the user interface is not consistent between the platforms. I found the iOS app easier to use. For example, sorting options appear on the bottom of the screens for the iOS app. On the Android app, it's a menu item.
If you are going to use the mobile apps to connect to your NAS540 remotely, you'll want to run the myZyXELcloud setup shown in Gallery 1 above. As noted, setup will create a DDNS account and attempt to set up port forwarding. ZyXEL relies on UPnP to open ports on your router and to redirect internet traffic intended for your NAS540 to the IP address of the NAS.
If you have UPnP disabled, you'll have to manually set up port forwarding on your router. In some cases, like mine, I have another network device that is already using port 80, so I had to set up an alternate HTTP port (ZyXEL recommended 8080). Normally, I keep UPnP disabled, but for testing, I turned it on so that it could properly self configure.
Once configured, you log into the NAS540 using either the Android or the iOS app. If you are on the same local network as the NAS540, either app will discover your NAS540 and prompt for your username / password. If you are attempting to connect to the NAS540 from a remote network and have set up myZyXELcloud, the host name will be in the format of username.zyxel.me. Of course, you can set up DDNS using other domains under Network->DDNS. If you have specified an alternate HTTP port for the NAS540, your host name will be in the format username.zyxel.me:port number.
The Android app will let you sort music by Folders, Artists or by track name. You can select individual tracks and add them to a playlist, but there doesn't appear to be a way to save the playlist. Selected files can also be downloaded to your Android device. For photos, you can sort either by date or folders. You can select individual images and play them in a slide show or download them from your NAS540. You can also upload photos to from your Android device to your NAS540. Slideshows of folders of selected images are supported.
Similarly, for video, you can sort by title or folders. You can select one or more files to download from your NAS540 or you can view your video. All of the features worked either on the local LAN or when connected via a remote network. I did run into video playback problems on my Android tablet, but that problem was probably related to the installed players on the device. I also installed the zCloud app on my Samsung S5 and video played back without a hitch. The gallery below will give you a feel for the Android zCloud app.
I installed the iOS device on my iPad and did my initial testing on that platform. While the application performed as expected on the local network, initially I had difficulty getting it to connect using a remote network - even though the Android app connected from the same remote network using the same host name and login credentials. At ZyXEL's recommendation, I uninstalled and reinstalled the iOS zCloud app, and that seemed to fix the problem. As noted, the features in iOS are very similar to those found in the Android app, but I found the UI on the iOS a little easier to use. Below you find a short gallery of screenshots from the iOS version of zCloud.