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The Sentinel DX4000 is inferior to Linux-based NASes in terms of HDD configurations. It only supports one RAID and the latter must be fault-tolerant. So, the basic configuration is a RAID1 built out of two HDDs. Our Sentinel DX4000 had two WD2002FYPS drives from WD’s RE4-GP series.

The OS takes 60 GB for its own purposes. With updates installed, we had about 40 gigabytes free from that amount.

Installing additional HDDs triggers automatic migration without data loss to a RAID5 built out of three or four HDDs. The Sentinel DX4000 is only compatible with a few models of enterprise-class HDDs, which is not convenient. The migration takes quite a long time: transitioning from two to three HDDs lasted about one day. A move from three to four HDDs took 30 hours. The NAS was accessible during that process but its performance was much lower than normal.

Oddly enough, the log entries about the start of the migration would be lost after its completion. The NAS’s log file has some other oddities, though. Updating information on the admin panel takes a few minutes, for example.

You can only get notified about urgencies via email. WD provides its own SMTP server to send such notifications but you can replace it with something else. If you’re using your mobile phone to receive them, you should be aware that the notifications are in HTML format with images.

It is possible to create shared resources which are represented as ordinary folders on the RAID array. Access rights can be assigned to individual users (including Guest) or for all users to read or write. There are no other options, which is normal considering the single available access protocol. NFS support is also declared in the NAS’s specs but the user manual and admin console do not have any mention of NFS. This service is not installed in the default configuration.

If you’ve got an external disk connected to the NAS, you can use it to create shared resources and assign access rights to them. The device's root directory cannot be accessed.

As for user accounts, you can use a local database or domain data. You can set up remote access options for each account individually. Admin rights can also be assigned.

One of the key features of the Sentinel DX4000 is its ability to automatically back up data from client computers which run the above-mentioned software. With appropriate hardware support on the client side, the NAS can even turn on the client PC remotely to perform a backup job.

When the client software is installed, the PC is registered in the NAS's database. You can then set up backup options on the PC or in the server's control panel. The backup jobs are carried out sequentially. After that, the server installs updates and reboots (that's what its documentation says). You can specify the operation schedule and backup mechanism in the service settings. By default, the backup procedure runs from 0:00 to 6:00. The NAS stores five daily, four weekly and six monthly copies of data. You can enter any number up to 99 into each field and specify the hour for the procedure to start.  

Take note that the NAS makes a full copy of a disk. You cannot choose particular data to back up. The service description says that deduplication technology is used to reduce the required storage amount.

Shadow copying technology provides additional options. Its settings are available from the standard admin console (by default, copies are created on a daily basis). This service is enabled for the system volume and user data. It helps users restore a required version of a file that has been changed.

The NAS has integrated means to set up, change or remove a password to access the HDDs as provided in the ATA standard. The key seems to be stored in the PCB's memory. If password-protected, the HDDs can only be accessed from this server unless you know the password. This feature doesn’t affect the HDDs’ performance.

The backup service allows you to create a bootable USB drive that can be later used to quickly restore client PCs by deploying a system disk image. The same method is used for the NAS itself. It can be helpful when installing an OS on to clean HDDs or when some failure prevents the OS from booting up.

We checked this feature out and found that it took over 8 hours to start up the NAS with two new HDDs. But we had to use two boot drive versions and press the reset button a few times, etc. So, the implementation is not handy. The manufacturer might have instead added an integrated flash drive with necessary data and/or use the NAS's own display and buttons.

In the Monitor section you can check out the current status of the NAS and its components. Information about model name, SMART parameters and temperature is not available for the HDDs. There is no option to turn off external HDDs safely.

Apple computers are supported as well. There is a special version of the client software for them but it refused to install on a Mac with the latest and up-to-date OS (saying that it’s already installed). In Mac OS X 10.6.5 the utility didn’t let us do anything, so we couldn't check out if its functionality differed from that of the Windows version. SMB-based access worked, though. Time Machine didn’t accept the NAS as a valid storage destination and some documentation only listed versions 10.5 and 10.6 as compatible ones.

The description you’ve just read refers to the basic version of the Sentinel DX4000. Its capabilities can be extended by installing certified modules from a catalogue available on the Microsoft website. Of course, you can try installing any other software, but you may have problems with compatibility or stability. At the time of our writing this the catalogue for this NAS offered about two dozen applications. Some of them enhance your NAS management options (for example, power management or remote management via a mobile phone). Others add new client-oriented services (iSCSI, ISO mounting, network printing, fax support). There are also complete server solutions for specific usage scenarios (sales system administration).

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