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NAS, DAS, Or What?

Comparing External RAID Housings
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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.

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  • 0 Hide
    rockbyter , August 14, 2008 5:19 PM
    did i miss the part about heat and noise?
  • 2 Hide
    Aragorn , August 14, 2008 5:56 PM
    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?
  • 0 Hide
    Anonymous , August 14, 2008 7:20 PM
    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.
  • 1 Hide
    hawler , August 14, 2008 7:32 PM
    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
  • 1 Hide
    Anonymous , August 14, 2008 7:59 PM
    @ 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.
  • 3 Hide
    njalterio , August 14, 2008 8:55 PM
    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.
  • 0 Hide
    Anonymous , August 14, 2008 10:19 PM
    @ 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!!
  • 0 Hide
    xxsk8er101xx , August 14, 2008 10:56 PM
    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.
  • 2 Hide
    GreenPower , August 15, 2008 12:23 AM
    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!
  • 0 Hide
    GreenPower , August 15, 2008 12:28 AM
    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.
  • 0 Hide
    Anonymous , August 15, 2008 12:59 AM
    @ GreenPower: No need for all that if you're using ZFS. ZFS has built-in CRC checking! No more need to worry about bad sectors or data corruption.
  • -1 Hide
    Luscious , August 15, 2008 1:14 AM
    I tried backing up a laptop one time with a measly 80GB drive using USB2.0 and it took me hours.

    All laptops should have an eSata port, especially if you've got a 200GB or bigger drive, otherwise you'll be waiting HOURS for a full system backup to complete.

    Of course, it all depends on HOW MUCH data you need to get backed up.

    Hard drives simply suck at backup, they are slow when it comes to transferring their full capacity and just as useless when it comes to having a backup that is durable/removable. Tapes are still the best way to go, they stream fast but have limited capacity and the drives are very expensive.

    Tapes need to come is 1TB capacities, they should cost no more than $100 a pop and the drives should be selling for no more than $600. I would not pay anything more for a tape system for home use. The problem is tapes are still targeted at businesses, which can easily pay the $2000+ price for the best drives.
  • 1 Hide
    Anonymous , August 15, 2008 1:44 AM
    Wow, it's been awhile since I've ran into a firewire evangelist. Let's hope they have better luck getting the next generation of fw on whatever they can because it seems to be largely only used for direct connections to equipment and that's about it.

    We've been using Express card or internal sata/esata on most of our macs in house and use them for the direct hard drive connections or even being used as a boot drive on the laptops. So far we noticed better sustained reading and writing performance with ESATA and the increase in the amount of enclosures and drops in prices have helped quite a bit also.

    Personally USB 2.0 is only an emergency connector. Only for a last resort. I've been known to take drives out of enclosures just to connect them internally then deal with USB.

    If any other connectors get more of a hold on the dv camera/audio equipment then firewire could be rather pointless. They have a nice connector but that's all I can really say in their defence when it comes to esata which is still rather fragile in my opinion.

    Either way, it's always nice to see what happens with the newer technologies. Optical connectors on usb3 is intersting, 10Gb ethernet way down the line and who knows, maybe the next firewire will be amazing. Competition is nice for our pocketbooks sometimes.
  • -1 Hide
    kenyee , August 15, 2008 2:10 AM
    timmah: if you've ever tried backing up to a hard drive w/ usb 2.0 and firewire, you'd know why I'm also a firewire fan though it sounds like you've tried backing up on usb 2.0 ;-)

    That said, esata is faster than firewire/400 (though only slightly faster than firewire/800 which most motherboards seem to lack)...
  • -1 Hide
    Anonymous , August 15, 2008 2:45 AM
    Another huge benefit of Firewire over USB is its power providing abilities. A firewire port provides roughly THREE times the power for external devices. You can run the latest, fastest, 7200 rpm drives bus-powered on a Firewire connection (several drives even!) but you definitely can't do that on USB. Heck, My HP laptop can't even power up a 5400 rpm 2.5" USB drive I have.
  • 2 Hide
    GreenPower , August 15, 2008 12:38 PM
    ZFS is for Linux. I use Acronis True Image for creating an exact image on a second hard drive for Vista64.
    A second motherboard backup strategy is necessary because of Windows anti-copy protection. PLAN to buy a SECOND identical motherboard. Only make your decision to actually buy it when its being discontinued. If the MB goes bad then your main HD backup is only of limited value. But if you put in an identical MB then you should be good to go!

    Hard Disks get corrupted and motherboards wear out. Plan ahead for these two major failures. Its just a matter of time.
  • 1 Hide
    itadakimasu , August 15, 2008 12:54 PM
    i suggested using an external sata solution for backups and was immediately shot down at work despite the cost and ease of data recovery vs tapes....

    the last time i need to restore something off the tapes, i needed to restore the server that the tape drives are located on and to do that I needed the tape software which had been lost, spent over 6 hours trying to re-install the backup exec software (alot of time due to it being an ancient machine w\ 10 minute restarts required periodically)
  • 0 Hide
    badboy4dee , August 15, 2008 12:55 PM
    For home use yeah HD backup makes sense as long as you have more than one backup. Rule is have more than just one HD backup and do it offsite, encrypted etc... . I know you guys must have heard of tapeless backups right?

    You go "anonymous guy" YOUR KUNG-FU IS GOOD.

    The Silent Majority
  • 0 Hide
    badboy4dee , August 15, 2008 1:03 PM
    GreenPower, I like using Winddows in a Virtual environment like VMware and the like and keep Micro$oft in it's place. Other option is to us Linux/wine/crossover and run Window appz on dat!

    The Silent Majority
  • 0 Hide
    badboy4dee , August 15, 2008 1:18 PM
    Cobian or Comodo both are free backups if you need the software

    The Silent Majority
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