I've just bought a new Miglia MediaBank HSR, and wanted to add to the other reviews of the product; largely because there aren't any good reviews.
The Miglia MediaBank HSR, which is an external firewire (IEEE 1394) drive. However, unlike other firewire solutions, this provides on-board RAID-1 mirroring between two hard drives. In fact, along with the HSR, the only other external RAID solution is the Wiebetech RaidTech external system. [The Wiebetech has a couple of advantages over the Miglia one; specifically, the Wiebetech has the option to use RAID-1 (mirrored) or RAID-0 (striped); it provides USB as well as FireWire; and the build quality looks better -- however, I didn't need (or want) RAID-0, and it's significantly higher cost than the Miglia.]
The reason I wanted to purchase an external RAID system was to solve performance problems on my Linux server. I'd used software RAID to mirror contents of drives, with the result that large data writes caused generic system inbalance. Obviously, I could have used a separate RAID card internally, but due to hardware support (and ability to come back up after a hardware failure), I decided that an external solution would be better for my requirements. In this case, if the computer I am using fails, I can just unplug the hard drives and put them into another system; if the RAID enclosure fails, I can just pull out the hard drive and use it in a single hard drive enclosure. So in any hardware failure, I can be up and running in a matter of seconds, rather than minutes.
The HSR stands for Hot Swap Raid; the drives are located in a drive caddy (tray), so I can pull out any drive from the system. When you insert a new drive, the on-board hardware mirrors the existing drive (overwriting the one you've just inserted) to rebuild the array; and as you might expect, you can still continue to read and write from the drive whilst the array is rebuilding. However, I wouldn't recommend using it during a rebuild if possible; the hard drive will churn as it tries to perform the mirroring and data access at the same time.
A key advantage of a mirrored system is that each drive can be used in a separate drive enclosure and give you access to all the data on the system. I have 3 drives, and swap between them; the 'spare' drive then becomes a backup snapshot of the contents of the drive when it was removed; thus, it can be used in an off-site backup (or in my case, a fire safe). It's a lot more comprehensive than a backup (CD, Tape, DVD) solution; because the data is stored in its own reading device and can be plugged in in seconds.
Using the FireWire 800 (IEEE 1394b) drive, I can read 1Gb of data in about 30s. The bottleneck of the data transfer is the firewire cable; so the speed benefits of a RAID-0 system aren't really applicable to an external system (hence why Miglia doesn't see the need for it). In fact, the only reason a RAID-0 system in an external enclosure is advantageous is to provide a larger single drive space; and in most cases, the OS will be able to do that with no extra cost. Obviously, this is using FW800 speeds; over a FW400 connection, the time taken to read 1Gb of data is about 60s.
I purchased the 3x250 Gb drive solution, and it takes about 2 hours to do a full mirror between the drive. It will take exactly this long regardless of how much datat here is, because it does a sector-by-sector copy of the drive; so whether there's data on there or not, the full mirror will replicate the contents of the drive completely. Of course, smaller drives will take proportionately less time; so the mirroring is about as fast as the hard drive load of about 1Gb mirrored in 30s. This suggests that the speed of the hard drive may be the bottleneck over a FW800 system; however, not by much.
- Write of 1Gb of data: 30s
- Read of 1Gb of data: 30s
- Backup of 250Gb mirrored drive: 2 hours
By not including a USB connection, Miglia are no doubt cutting out a part of the market. However, most of their existing product line are firewire solutions or video processing, so no doubt may be Mac oriented. But the drive does work with many OSs -- the unit presents itself as a single external FireWire drive; so a Linux, Windows or Mac machine with a FireWire (IEEE 1394) port will be able to use this drive.
Some terminology (and speeds) for those that are interested:
- USB 1, aka Low Speed
- Mostly good for devices such as keyboards, mice, and low-data transfer solutions. Limit of about 1.5 Mbps
- USB 1.1, aka Full Speed
- Mostly good for external hard drives, cameras etc. that need to transfer larger amounts of data. Limit of about 12 Mbps
- USB 2, aka HiSpeed or High Speed
- Mostly good for external hard drives; allows for a much faster transfer of data between host and controller
- FireWire aka IEEE 1394 aka iLink
- Apple's trademarked term for the IEEE standard (also called i.Link by Sony, and appeared on most of the PS/2 range but largely underutilised)
- FW400 aka IEEE 1394a
- The 'original' firewire. Supports rates of 400 Mpbs. Came out at a similar time to USB 1, so most large-volume devices (e.g. video cameras) had IEEE 1394 inputs and outputs. Additionally, some cable companies are providing IEEE 1394 ports to access data, and some HDTV systems have an IEEE 1394 input. Has enough data transfer rate to support decent quality video in real time; hence, Apple's iSight is a much higher quality camera than most USB webcams
- FW800 aka IEEE 1394b
- The 'new' firewire. Supports 800 Mbps. Came out before USB 2, so whilst USB 2 is faster theoretically than FW400, FW800 beats it into submission.
Whilst USB 2 was a tack on to the end of the USB spec; FW800 is part of an on-going speed increase in the firewire specification and IEEE 1394 specification. It should result in multi-gigabit speeds eventually (1600 mbps). A good visual comparison of speeds is available at the Mac Speed Zone.
FireWire has also been historically pushed by Apple in the audio and video solution market, so it may be no surprise that the European DVB group has chosen the FireWire interface as the digital video interface of the future.
It should also be noted that USB is a device-to-computer link, whereas the FireWire is a computer-to-computer link. That is, multiple computers can be shared over the same FireWire bus; and indeed, there is a specification for IP-Over-FireWire (which is available in all Macs) that allows two mac systems to use FireWire for networking. FireWire-to-FireWire network bridges are actually faster than 'fast' 100 Mbps networking; additionally, ethernet never gets up to full utilisation of bandwidth, whereas the FireWire is much closer to achieving the theoretical maximum. As a result, FW800 networking is pretty much as fast as gigabit networking is.