Mediasonic HFR2-SU3S2 PRORAID 4 Bay 3.5" SATA Hard Drive Enclosure - USB 3.0 & eSATA

I have two of these boxes; both are configured as RAID boxes and have been in continuous use for years -- one of them since 2013. (One is RAID 10, the other RAID 5.) In that time I have had to replace three hard drives in the in-use units. At various times each box have been moved between USB and eSATA connection to the host PC. Both have always been consistent, solid performers. Neither has ever given me any trouble.WHAT IT IS: This is a simple and cost-effective external device. It functions well in either USB or eSATA mode. The box is self-contained and plug-and-play; it requires no drivers and adds little or no extra load to the host PC. I have never had a PC or Mac (with appropriate configuration) fail to recognize the box and "talk" to it as expected. In any RAID configuration, it appears and behaves just like any external hard drive. As JBOD, it shows up as multiple separate external devices. Within the limits of what it is and how it works with the connected computer (discussed more below), it just works and has always been extremely reliable. But you should think through what you are getting at this very economical price point (economical for a RAID box, that is).The device detects the power state of its connection to your computer; it will turn off automatically when you power down your computer and will power back up when you turn the computer back on. This is a FEATURE and is the intended operation. You do NOT have to turn it off and on manually. For many this is a great convenience. It is also a good thing for power and heat saving (as well as hard drive life span and reducing noise when the computer is not on). But it can also be a negative depending on your use case (more on this below).In either SATA or JBOD or using eSATA or USB, I have never had a lick of trouble; the box just works. Lights on the box correctly indicate drive use and will tell you when a drive has failed. Power down and replace the failed drive; when you power back up in RAID mode the box will proceed to rebuild the array with no further action from you. (In JBOD mode, the new drive shows up in your operating system -- though of course you may need to go into disk manager to partition and format it before Windows can use it.)In terms of value for money, the performance is great for this price.WHAT IT IS NOT: You do get what you pay for. This is a very economical / cost-effective unit (for a multi-interface RAID unit).The device talks via eSATA OR USB. Most home-user class computers will not let you use both interfaces at the same time. For example: If you connect both at the same time, a Windows PC will only recognize the device on the eSATA connection (since the SATA bus is usually initialized before USB).Though the device does accept SATA III hard drives and works internally at 6Gb/sec speeds, it can only sustain those speeds to your computer when configured as JBOD. When configured for RAID it can only support 3 Gb/sec speeds (equivalent of SATA II, closer to USB 2 than 3 speed). That makes it great for backup and fine for accessing files one at a time (even playing music), but maybe not really solid for video streaming or disk-intensive gaming applications.The ventilation system is less than spectacular and needs to be kept clean or else lint buildup will make airflow a drive-killing problem over time. When closed up properly, the automatic fan settings on this box will make the drives inside tend to run hot (using HD Sentinel to monitor individual drive SMART temp reporting). That said, I have run these units for years on end without encountering unexpected / premature drive failure. I have also found the manual "high" fan setting works pretty well and is still pretty quiet -- not really noticeable if sitting under the desk. The unit will also run just fine with the front door down (open), which will cool everything down and keep it at more "normal" HD operating temps. The box front can be opened and closed without disturbing the drives inside while the unit is running (just be careful not to jiggle or move the box itself or drives inside while running). All box functions work just fine when the front is not closed, if you want increased cooling. (Just don't forget you left the box open when you are working around it or go to move it!)This box will NOT magically transform all the vagaries of PC external connectivity into the reliability of permanently connected internal drives. It is NOT a high-end NAS or internal RAID system powered by an expensive and high-capacity controller. All bets are off if you move the unit and/or accidentally jar or disconnect the cable when the unit is running -- or if your computer's power saving settings turn off the connection to this unit. I have found the system works consistently as designed as a solid SATA II drive when connected via eSATA or USB (assuming the cable isn't accidentally jolted loose).You can use this box and it will be reliable attached to an always-on computer -- but first you need to expect to spend configuration time and might encounter some frustrations along the way. To get reliable, always-on connectivity with no unexpected disconnects, you are going to need to spend some time checking your computer BIOS and several settings in the operating system. Power saving settings that shut down your hard drives (SATA) or dormant devices (USB) will work just fine with internal and some external devices, but I hope it is obvious that they will cause this box to turn itself off. When the connection gets powered down, the device will see that as your PC turning off and in response it will turn itself off (which is exactly what it is supposed to do, as mentioned above). Since the device is driverless, there is no software to keep it alive or magically reconnect it when/if you return and want to use it. When that happens, the only recourse is to power down your PC, then restart. It took me several tries to find and disable the various PC and operating system power-saving features; once I did that -- ensuring the PC / operating system did not time out / turn off its USB or eSATA connections -- the Mediasonic box became absolutely solid and reliable, working predictably in harmony with the PC to which it is connected. Once everything was configured, it became another always-there drive that just.plain.works.As noted, this device does not come with external monitoring/control software. Out of the box, you need to look at the lights on the front to affirm it is configured and operating properly. There is no software pop-up or alert on your computer desktop if your RAID array is degraded -- you have to actually look at the box. If you forget to look at the box, you might not notice a drive has failed until it's too late to rebuild the RAID array. On the flip side, those lights on the box do correctly indicate hard drive activity inside the box and do indicate if a drive has failed (or, once you replace the failed drive, when a RAID array is rebuilding). The lights are accurate but do not give you much of an indication as to progress of built-in functions; you're not going to get much of a clue as to how much longer that RAID rebuild is going to take.However and FWIW. I have found this device does correctly pass all needed information through for most disk diagnostic applications. HD Sentinel works well and accurately to report the status of every constituent disk drive (even when configured in RAID mode so that Windows thinks its just one big drive). I have also found by trial and error that several software distributions that come with other external RAID systems will also correctly read and report status of these boxes -- thought they still won't let you remotely configure or adjust what the RAID controller is doing. (For example, the software that comes with Sans Digital units will read and report on these Mediasonic boxes when configured as RAID units.) Your mileage may vary.Overall, this box is everything I had hoped and I have found it completely reliable. A bargain at a $150 price tag.

This is a beautifully engineered product that simplifies the installation and operation of a complex sub-system delivering astonishing price-performance.I recently upgrade the RAID 10 storage on my workstation system (Supermicro 5036T-T) to use use 954GB SanDisk X400 SSDs instead of WD 10KRPM HDDs. So what am I going to do with four of these replaced high-performance mechanical drives? Why not put them in an external array enclosure? That's when I bought the Mediasonic HFR2-SU3S PRORAID 4-Bay enclosure.DO NOT CONFUSE this on-board RAID controller model with the similar looking ProBox HF2-SU3S2 which uses a port multiplier to attach 4 drives to a PC through a single data transfer connection. Here's why: with the on-board RAID controller, the OS issues a single read or write IO operation through the cable to the external PRORAID box which then takes care of managing the multiple RAID operations which requires at least 4 IOs to the independent disks. With the less sophisticated ProBox unit, the PC must issue at least 4 IOs through the cable--one for each disk (this is all hidden from the applications and user, of course). Even though the unit uses FIS multiplexing to initiate parallel operations, the individual disks maintain their identities and therefore reduce the throughput of the external cable by 4.This is a carefully engineered and designed product, BUT YOU NEED TO READ THE DIRECTIONS CAREFULLY (!!!!!!!!!!!) BEFORE installation. There are a number of steps that must be followed, but the directions are clearly written with useful illustrations (and in proper English). There are so many well designed aspects that aid the end user that it could make a review three times as long (when I say design, I don't mean just the visual aesthetics but overall systems design including hardware--mechanical and electronic--software, and integration--this is a fully functioning independent sub-system--and documentation).The buttons, indicators and labels are all obviously carefully considered. Note: there is a hidden button on the back of the unit behind a cover that must be opened and used to complete setup of the RAID. This design prevents the inadvertent changing of the RAID type which would cause the accidental loss of data. This interlock does, however, provide an extra but useful step that could confuse the someone if they do not READ THE INSTRUCTIONS CAREFULLY AND FULLY BEFORE BEGINNING. I write this advice not because the instructions are confusing--quite the opposite--but because this is a sophisticated product that requires several levels of configuration in order to set up the physical and logical structures required to integrate seamlessly with the OS. I don't know how they could have made this easier--it is very well done. There are a lot of great features that I could write about now, but I suspect it is a level of detail that would make this review less readable. I think I can summarize that by borrowing a term from the digital camera market: this is clearly a Prosumer (professional/consumer hybrid) product that is nearly commercial in its quality, but accessible to the consumer market.So, one more potentially interesting observation. This unit offers two types of external cable connects between the computer system and the external RAID: USB 3 and eSATA 3Gbps. On the box is clearly displayed that USB 3 transfers at up to 5Gbps and eSATA up to 3Gbps. However, transfer speed IS NOT THE SAME as throughput which is the effective overall transfer rate end-to-end including delays in media arbitration, the OS system functions, and various other components incurred as a result of initiating the large number of operations usually required to complete actual the data transfers encountered during system operation. As a result, I tested both link interfaces using a simple test: repeatedly copying a 2.2GB file from the PC's SSD to the empty external logical drive created on the PRORAID unit.(Full disclosure: these results may have been influenced by the controllers through which the transfers took place. The USB 3. is connected through a Renesas Electronics PCI-e Host controller, and eSATA is connected through an IOCREST (SiI3124) PCI-X controller.) Overall, the slower rated eSATA link has considerably higher write throughput of 314 MB/s compared to the USB link with a throughput of 110 MB/s. This was a convenient test to run because access to the PRORAID storage is transparent to the link type. All I needed to do was switch the cables. How nice is that?!