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The PX-NAS4's RAID features are a bit different than normally found in consumer NASes. The most notable difference is that you create RAID arrays first, then volumes in those arrays. You can have multiple volumes in a RAID array. But you can't dynamically resize those volumes.

The NAS supports RAID expansion, but not RAID level migration. You can add drives to existing JBOD and RAID 5 arrays only, without disturbing existing data. Drives that can be added include external eSATA drives. Once the RAID array is expanded, you then increase volume sizes(s).

You can also expand RAID 5 arrays by replacing drives one at a time and letting the array rebuild. You only get a capacity increase when all drives in the RAID array have been replaced.

Media Serving

The PX-NAS4 provides typical DLNA and iTunes streaming support. These worked well enough out of the box, and once I had configured the the "Media Server" section of the admin, I was streaming files to my Xbox360 with relative ease. An interesting sidenote: Microsoft appears to have updated their media player with more support for MP4 files, as most of my collection is in that format to support H.264 and my Apple devices nicely.

NAS Vendors really need to be clearer about their Xbox360 / PS3 DLNA "support". Even though the Xbox360 and PS3 have been getting better at streaming files, there is still notoriously bad support for things encoded in unsupported codecs, or unsupported file containers.

For example, DivX and XviD support is virtually non-existent, and many files are still encoded in these older codes. NAS vendors should stipulate that DLNA "support" means the ability to index your media files and present them so that DLNA-only devices can see them, but not necessarily be able to play them.

iTunes streaming worked fine as is usual for NASes. But there are no separate controls for iTunes and DLNA servers, and no indication that the "Media Server" actually controls both services. I did have some initial trouble getting videos to show up, and ended up having to rebuild the database. This could be a long process for people with large collections, but didn't seem to happen much afterwards. Note that only a manual scan can be initiated; there is no automatically scheduled scan.


The PX-NAS4 has a number of interesting backup options. One interesting perk is the ability to use other NASes' SMB / CIFS shares as backup targets. NETGEAR has offered this for some time on its ReadyNASes, joined by Iomega more recently.

The downside is that this Archive type backup creates a DAR format file, which will be familiar to Linux users, but not so much to Windows and MacOS fans. It would have been much better if backed up files and folders were copied as-is for easy recovery. At least Plextor provides a built-in recovery mechanism for these Archive backups.

Archive backup setup
Figure 3: Archive backup setup

Also available is a Synchronization backup to another PX-NAS4. The protocol used isn't specified, but we're guessing it's a slightly customized form of rsync, which is a method used by other NAS manufacturers. Unfortunately, we could not get it to connect to a standard rsync server because there is no place to enter an rsync module (target folder) name. So you have to buy another Plextor NAS to use the synchronization type backup jobs. Synchronization backups can be compressed and sent via an encrypted connection and you can also set a bandwidth limit.

A third backup type is Snapshot, which makes a copy the entire selected volume at scheduled intervals. Snapshots are stored in a special image file type, which Plextor includes a recovery option for.

The last backup feature of note is support for Apple Time Machine. As I noted earlier, AFP support is required to support Time Machine backups, but Plextor doesn't support AFP. So how do they support Time Machine?

Time Machine Hack
Figure 4:Don't try this at home, kids.

It turns out that in the user guide, Plextor instructs Mac users perform a hack at the command line (Figure 4) that enables unsupported network shares for Time Machine. This is a undocumented command and generally not recommended for production environments, because AFP supports HFS+-only file system features like resource forks.

Enabling completely undocumented and unsupported share types for Time Machine is not for the feint of heart (or smart for that matter). So I would not count on using a Plextor NAS for Time Machine backups until Plextor supports AFP.

Drive Pull Test

Failed Drive
Figure 5:Don't expect too much information from the hard drive indicators themselves in a failure.

I did not bother to remove the case for internal pictures as Tim already covered this in his New To the Charts review. I did, however, perform a drive pull test, to see how the device responds to a drive failure. I tested by starting a large folder copy, waiting a bit, then pulling a drive. Shortly after the pull, the file transfer stopped for about 5 seconds and then continued at a degraded speed. (The Windows 7 file copy window reported a drop from 50 MB/s to 35 MB/s.)

Shortly after the pull, the PX-NAS4 starting beeping, similar to how a UPS might beep when on battery, but a little slower. Unfortunately there's no front panel button to disable the buzzer. So I had to log into the device and go to, of all places, the log configuration page!

I reinserted the drive, hoping the buzzer would silence, but it did not. I ended up silencing it via the web interface, which is annoying because you have to remember to re-enable it once the array is restored. Also, restore did not start automatically and required manually initiating the repair from the SATA Disk > RAID configuration submenu.

The array rebuild, once manually restarted, took about an hour and a half. Files were still available during this time.

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