Original Link: http://www.anandtech.com/show/6128/mediasonic-probox-8bay-35-usb-30-esata-das-review


Prior to the rapid rise in popularity of Network Attached Storage (NAS) devices, consumers used to store large amounts of data on Direct Attached Storage (DAS) units. While USB 2.0 and Firewire used to be the interface of choice earlier, neither of them could maximize the bandwidth capabilities of the storage units (HDDs). USB 3.0 and eSATA serve the current day consumers in a more efficient way. We believe that the adoption of Thunderbolt in computing systems will make DAS units more relevant as the days go by. Today, we will take a look at the Mediasonic H82-SU3S2 3.5" USB 3.0 / eSATA Probox 8-bay external hard drive enclosure.

Mediasonic's H82-SU3S2 is a branded version of ODM manufacturer Hotway's H82-SU3S2, and utilizes a bunch of JMicron bridge chips. The unit is capable of being connected to the PC through either USB 3.0 or eSATA. The latter case needs a port multiplier aware SATA host controller on the PC side if more than one drive bay is being used. The operation is in single mode (JBOD) only, making the unit quite straightforward to use for the consumer.

Testbed Setup

Despite having a variety of systems with eSATA ports at my disposal, I was unpleasantly surprised to discovered that almost none of them had port multiplier capability inbuilt. These included boards based on the H55 and H65-M Intel chipsets as well as the AMD A50-M Hudson-M1. The A75 chipset in the ASRock A75 Pro4 supposedly has port multiplier capability. Unfortunately, ASRock confirmed that the current BIOS for that motherboard was not capable of supporting port multiplication.

In the process of sifting through the rest of the systems at my disposal, I found that the eSATA port on the Asus P8H77-M Pro that I had used for testing the HTPC credentials of Ivy Bridge was not from the H77 chipset, but, from a Marvell 88SE9172 SATA host controller. Though Asus doesn't specifically claim port multiplier support in the board, the data sheet for the Marvell controller indicated that it was compliant. In my initial testing, the port multiplier feature didn't work, but reinstalling the Marvell Magni driver after setting the eSATA port to be in AHCI mode resolved that issue (to some extent). There were no such issues with USB 3.0

Mediasonic Probox 8-bay eSATA / USB 3.0 DAS Testbed Setup
Processor Intel Core i7-3770K - 3.50 GHz (Turbo to 3.9 GHz)
Intel HD Graphics 4000 - 650 MHz (Max. Dynamic Frequency of 1150 MHz)
Motherboard Asus P8H77-M Pro uATX
OS Drive Seagate Barracuda XT 2 TB
Secondary Drives Kingston SSDNow V+ 128 GB SATA II SSD SNV325-S2/128GB
Corsair Performance 3 Series SATA III SSD CSSD-P3128GB2
Memory G.SKILL ECO Series 4GB (2 x 2GB) SDRAM DDR3 1333 (PC3 10666) F3-10666CL7D-4GBECO CAS 9-9-9-24
Case Antec VERIS Fusion Remote Max
Power Supply Antec TruePower New TP-550 550W
Operating System Windows 7 Ultimate x64 SP1
Display Acer H243H

From the perspective of the Probox enclosure, two sets of SATA drives were used. OCZ provided us with some Vertex 4 64GB units for our NAS testbed (about which I will be writing soon), and I took the opportunity to sneak in eight of them for evaluating the Probox before embarking on that build.

For meansurement of power consumption and performance under normal usage scenarios, a few mix-and-matched 7200rpm 1 TB hard drives (from Samsung and Seagate) were used.

In the next section, we will briefly go over the internals of the Probox and the build quality.


Build Quality and Internals:

The Mediasonic Probox 8-bay JBOD enclosure comes in a spartan package with just the bare necessities. The most important aspect of the package is the absence of an external power adapter. The PSU is internal to the unit. The contents of the package are as below:

  • Probox main unit
  • 1x eSATA cable
  • 1x USB 3.0 cable
  • 1x power cord
  • 8x plastic HDD handles and 16x screws for the handles
  • 2x keys for the door to the HDD bays
  • Screwdriver
  • Quick Installation Guide leaflet

The gallery below shows some pictures of the main unit. The unit is quite hefty at around 10 pounds without the hard drives installed. The dimensions of the main unit are 15.5cm x 25.3cm x 35.2cm. There are two internal 80mm fans which can be replaced by the user.

There are no HDD trays, but just plastic handles. The handles are also too flimsy for my liking. This means that 2.5" HDDs / SSDs are a no-go. I tried using a 3.5" adapter that is usually bundled with the SSDs, but the SATA connector on the mounted SSDs don't align up with the fixed SATA connector inside the Probox bay.

We managed to grab some photographs of the chips inside the unit. Three of them turned out to be JMicron bridge chips, as shown in the gallery below.

The main chips in the enclosure are:

JMS539: The JMicron JMS529 is a USB3.0 to SATAII 3Gbps bridge controller. It integrates a 60MIPS 8051 microcontroller along with 1 USB 3.0 PHY and 1 SATA PHY.

JMB321: The JMicron JMB321 is a single chip which integrates 6 SATAII 3 Gbps PHYs along with a host microprocessor. The firmware can configure it either as a 1-to-5 port SATAII port multiplier or 5-to-1 port SATAII selector. The Mediasonic Probox contains two of these JMB321 chips, using them in port multiplier mode. These two chips are used in cascaded configuration, with the output of the second one being routed either to the eSATA port or the JMS539 depending on the selected interface. As expected, simultaneous access of the SATA drives over both eSATA and USB 3.0 is not possible.

EM78P520: This microcontroller from Elan Microelectronics is used for overall housekeeping purposes.



Performance Benchmarks:

In order to evaluate the performance of the enclosure, we used SSDs under the impression that they would deliver better performance compared to HDDs. We mentioned initially that the Probox doesn't support 2.5" drives. However, with careful manual handling, 2.5" SSDs could be connected to the internal ports with the unit laid sideways (to avoid the SSDs hanging off the internal SATA connectors).

The following IOMeter benchmarks were run in both eSATA and USB3 mode for configurations involving disks in 1, 2, 4 and 8 bays.:

  • 128K Sequential Accesses with a queue depth of 1
  • 4K Random Accesses with a queue depth of 3
  • 4K Random Writes with a queue depth of 32

Despite my intent to benchmark all possible configurations for both eSATA and USB3, I found that the P8H77-M Pro's eSATA port would BSOD frequently whenever we had more than 2 drives being accessed using its port multiplier feature. Any missing bars in the above graph indicate that the test couldn't complete because of this issue. In fact, Mediasonic strongly recommends PCI-E add-on cards with Silicon Image 3132 / 3124 chipsets which have support for FIS based switching with port multiplier.

In addition to the above benchmarks, we also ran the DiskBench tests that we use in the NAS reviews. The graphs below present the results obtained in the four tests.

One of the main issues I found with SSDs was the increase in I/O response time when multiple disks were being simultaneously accessed through IOMeter. I found this mainly during access through USB 3.0. The issue may be present even in the eSATA configuration, but I am unable to confirm it due to the port multiplier issue.

In the configurations under which eSATA worked, it seems to have a steady increase in performance as more disks are accessed. Through USB 3.0, however, the performance seemed to plateau very soon. Was this something specific to SSDs or would it manifest itself even with HDDs? The next section tries to analyze this further.

Power Consumption and Miscellaneous Factors:

In the typical usage scenario, the Probox will be used with 3.5" hard disk drives. A majority of the end users plan on using a DAS unit to store multimedia files. Typical access to these types of files involves sequential reads and writes. In order to evaluate performance and power consumption under these typical usage conditions, we used 7200rpm 1TB HDDs and ran 128K sequential access tests with high queue depth using IOMeter. The results are presented below. As seen in the previous section, USB 3.0 performance seems to plateau, while eSATA seems to be able to deliver much better performance. eSATA is unusable for configurations with more than two drives.

Despite being advertised as being able to provide 5 Gbps of bandwidth, the USB 3.0 port is obviously held back by the 3 Gbps limit of the SATA side of the bridge chip. In practice, both the read and the write bandwidth seems to be limited to around 180 MBps. On the other hand, eSATA seems to be able to reach as high as 240 MBps and probably has the ability to even perform a bit better with a suitable eSATA port. We may update the piece after the receipt of a suitable eSATA add-on card.

The table below presents the power consumed at the wall (as measured using a Watts Up? Pro meter) under various conditions. In the table below, the access column refers to 128K sequential reads and writes with a queue depth of 64. The average of the numbers obtained for reads and writes is presented. Between USB 3.0 and eSATA in the 1 and 2 disk configurations, we found that the power numbers were different by only a few tenths of a watt. Therefore, all the numbers presented below are for access through the USB interface

Mediasonic Probox 8-bay Single Mode DAS Enclosure Power Consumption
Turned Off 0.6 W
No Disks / Min. Fan Speed 12 W
No Disks / Mid. Fan Speed 13 W
No Disks / Max. Fan Speed 15.9 W
No. of Disks Idle Access (Min. Fan Speed)
1 17 W 19.7 W
2 22.7 W 26.8 W
3 28.1 W 32.8 W
4 33.5 W 39.7 W
5 39.4 W 46.5 W
6 44.9 W 52.5 W
7 50.1 W 59.0 W
8 55.6 W 65.1 W

The two fans in the unit can be put under manual or auto control. The auto control is enabled by thermal sensors and the feature works well in practice. There are three fan settings. In such units, the fans are the most likely components to fail first. Thankfully, they are quite easy to replace and Mediasonic doesn't void the warranty when users replace the fans themselves.

The unit also has sync settings which enable it to power on and off in tandem with the computer's power state. The hard disks are also allowed to go to sleep as per the drive's firmware settings (the duration can be modified for most disks using the smartctl utility).

Some users have reported problems with the USB 3.0 connection having issues, but we didn't encounter any issues in our stress testing. We can only conclude that the USB 3.0 ports on the H77 chipset / Intel's USB 3.0 drivers don't have any issues in interacting with the JMicron USB 3.0 to SATA bridge.

Final Words:

As we come to the business end of the review, we will summarize the pros and cons of the Mediasonic Probox 8-bay JBOD unit first.


  • Provides quick access to upto eight 3.5" SATA HDDs
  • Fulfills basic functionality without flaws and has decent performance
  • Dual interface (eSATA and USB 3.0) support
  • Automatic fan control and ability to turn on and off along with the PC


  • eSATA is unusable for configurations with more than one drive unless SATA controllers with port multiplier support are used. Even in that case, only add-on cards using the Silicon Image 3132 / 3124 controller can access all the eight drives using the port multiplier feature (standard specifications seem to call for support of upto 5 SATA devices only through a port multiplied link)
  • For the pricing of the device (more than $250), an add-on card with the appropriate Silicon Image controller must be bundled
  • The unit forsakes support for 2.5" HDDs / SSDs, and the latter don't work even with 3.5" adapters. The only way to solve this issue would be for Mediasonic to bundle a tray capable ot supporting both 2.5" and 3.5" HDDs and slotting in perfectly with the fixed SATA connectors inside the unit.
  • The bridge chips conform to the SATA 3 Gbps specification only, and USB 3.0 port is unable to deliver full performance. With eight drives being accessed simultaneously, it is quite easy to saturate a 3 Gbps link. Bridge chips capable of 6 Gbps support would definitely become necessary when DAS units with SSD support come to the market.

Motherboard vendors should also make sure that their eSATA ports conform to the port multiplier specifications. However, the rise in popularity of USB 3.0 probably means that vendors don't want to spend too much effort on this. Thanks to its dual interface, the Mediasonic Probox enclosure is compliant with a wide range of systems. It should be able to satisfy the needs of most consumers looking for a 8-bay JBOD enclosure.

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