Comparing External RAID Housings

Features
By Marcel Binder
published

NAS, DAS, Or What?

The products tested in this article are pure Direct Attached Storage (DAS) devices. To be able to use a DAS device, you must be connected to a computer which has the appropriate controller. The storage capacity on the external unit is, first and foremost, only available to the user of the computer to which it is attached. To enable other users within the network to access the external storage unit, this must be explicitly made possible using the Windows Release function. DAS devices do not have an operating system, unlike Network Attached Storage (NAS) devices, which usually do.

NAS devices are not connected to a computer—they are always connected directly to the network. Access control and the configuration of the drives are taken care of by the integrated operating system, which can usually be controlled via a web interface. NAS devices are characterized by the fact that they have various RAID modes that can be used to operate several drives in a cluster. This helps to ensure that, in the event of one disk failing, the functioning of the NAS device itself is not affected.

Support for various RAID modes with NAS devices can be considered standard today, but DAS devices are increasingly also offering this functionality.

External RAID via eSATA and USB

Thanks to the intelligent SATA controller, which, alongside the port multiplier also provides a virtualization layer, multiple drives can now be addressed simultaneously in a single housing via either eSATA or USB 2.0. The operation of an external RAID cluster in the DAS devices is thus possible. To operate a RAID configuration, it is necessary for the housing to be used with at least two drives.

Marcel Binder
Marcel Binder
25 Comments Comment from the forums
  • rockbyter
    did i miss the part about heat and noise?
    Reply
  • Aragorn
    Did anyone else think that the thumbnails of the charts were utterly useless. Why don't we get nicely sized images in THG reports anymore?
    Reply
  • Discussion about external desktop storage and no mention whatsoever of Firewire? *yawn* call me when you have a serious storage article. Firewire is the defacto standard in the pro desktop market, and also of course with all Apple systems. It's faster than USB 2.0 in every benchmark. It's more flexible and mature than eSata. And with Firewire 3.2 Gb/s coming later this year, it's about to get reeeeally fast. I have five external disks (including 2 raid arrays) and all are Firewire 800 connected.
    Reply
  • hawler
    I wish firewire would just die with the upcoming release of USB 3.0 which will be fast 4GB/s and more common. It really is annoying to have both of these on a computer when you could simply have just one of them. Id rather have 10 USB slots then 8 USB and two firewire on my computer. I knwo this isn't goign to happen but there simply is no need to have both, I realize currently it is faster but it won't be soon, and when it was first made they should have tried to make it a new version of USB so that there wouldn't be 2 standards.

    Thats just my opinion on it, im sure people who use a lot of firewire products (i only use it for my ext HDDs but) might disagree but the idea of having just one I/O choice to me is better...its like display port for monitors...why oh why didn't they just leave it with DVI/HDMI
    Reply
  • @ hawler: USB is NOT a replacement for firewire! There's a reason that ALL pro audio equipment uses Firewire instead of USB. There's a reason that ALL camcorders can stream video only over Firewire and not USB.

    It's called "Isochronous transfers". Critical when you're dealing with real-time audio or video. USB doesn't provide that. Also makes bulk data transfer (like backups, for instance) perform more consistently.

    USB was never designed for bulk data transfer. That's why it sucks so badly at it. Ever wondered why a 480 Mbit USB2 connection (That's 60 MB/s) can barely achieve between 35 MB/s in real world transfers? That's because the protocol sucks at bulk data transfer. USB was designed for keyboards and mice. To replace low-speed serial ports. Not for high speed bulk data transfer. The USB protocol is inherently deficient in this regard.

    Firewire, on the other hand, was designed *specifically* for bulk data transfers. It's obvious when you look at its efficiency at these kinds of tasks. Firewire 400 (that's 50 MB/s) achieves around 42 to 45 MB/s in real world performance. Far FAR more efficient than USB at moving data.

    My vote would be for ALL external data storage, audio, and video devices to be firewire only. Make everything else USB.
    Reply
  • njalterio
    For those of you asking about firewire, many companies do not like to use firewire because of security issues. Firewire devices communicate through direct memory access. There is no operating system intervention. This is why many companies will have their IT staff remove firewire expansion cards or disable them.
    Reply
  • @ njalterio: Companies? IT departments? What kind of company IT department directs their employees to backup the PC's individually using external disks??

    Firewire does indeed use DMA. That's another advantage it has over USB, at least in terms of performance. Everyone knows from back in the PATA disk days, that DMA transfers are way faster than non-DMA transfers.

    But for professional audio/video, there is only one option and that's Firewire. No such thing as pro a/v products that use USB. They just don't exist. So when you say that "companies disable fw interfaces" I suppose it depends on what sort of company you're talking about. Not a production studio that's for sure!!
    Reply
  • xxsk8er101xx
    There is this program called Hotswap 4.0.1 i think it is. or maybe 4.1.1. I forget. But it's called Hotswap and it allows you to have that add/remove icon for harddrives. It works for cd-roms, ide drives, fixed drives ... it's an amazing program and best of all - it's free!

    Again it's hotswap! 4.'something ... http://www.softpedia.com/get/System/OS-Enhancements/HotSwap.shtml it's an amazing tool and it works very well. Solves the problem listed on page 1 about no add/remove icon.
    Reply
  • GreenPower
    All my applications are installed on the C drive, which is a 500GB $79 WD unit. I buy a second identical drive and hook it up to an extra 18" sata cable and power right at the edge of the pc case chassis.
    I use Acronis True Image disk utility to make and exact copy when the system half way reboots. Then I turn off the power and swap disks. A few applications like Photoshop can still detect they have been copied. But besides this its a 5 minute replacement if my HD ever gets corrupted.

    Otherwise it takes about 4 LONG days to rebuild the system from scratch.
    Five minutes vs four days. Go figure!
    Reply
  • GreenPower
    Always run the long format and surface scan any new disk to check for bad sectors. Then re-scan it after its been copied and re-booted with. Only then can you state that you backup is worthy.
    Reply