Building a Mac DAS

Discussion in 'Mac Accessories' started by radiogoober, Jul 1, 2012.

  1. radiogoober, Jul 1, 2012
    Last edited: Jul 1, 2012

    radiogoober macrumors 6502a

    Jun 7, 2011
    Hi all,

    I am trying to figure out how to build my own DAS. I say DAS instead of NAS, because I already have a Mac mini server that acts as a file server, but my storage situation there is messy.

    Currently attached to my Mac mini server:
    - WD MyBook Thunderbolt Duo (2 x 3TB disks, JBOD)
    - WD MyBook FW 800 3TB disk
    - 2 x 1 TB USB2.0 disks

    Currently, the first 3TB disk in the WD Thunderbolt Duo is my media drive. The data there is replicated by Carbon Copy Cloner (a rsync front-end) to the second 3TB disk, and also to the FW800 disk, which gives me two complete copies of my media.

    I'm rapidly filling up the 3TB disk, so I want to upgrade to something more spacious. I'm paranoid about data loss, so I want to upgrade to something that will give me at least 1 full backup of my data. I'm interested in a RAID5 or RAID6 setup, but duplicated. My thoughts were:

    2 x RAID5 setups - Being RAID5, if one disk fails in the array then the array can be repaired. In the off-chance that the RAID5 array fails completely, then I'd have a whole backup of the array in a second RAID5 array.

    2 x RAID6 setups - The same logic as above, but with the dual disk redundancy that gives me an extra layer of security, which decreases the chance that I'd ever have to actually depend upon the second RAID6 setup.

    I want about 12 TB of storage.

    (Note: I am aware of things like CrashPlan, but they only allow you to seed a single 1TB drive, and my internet service caps at 220 GB / month, which means it'd take me literally years of utilizing all my bandwitch to upload multiple terrabytes of media.)

    I've read lots of wonderfully written articles about setting up these types of file servers with a Linux box. However, I'm interested in taking a different approach. I already own a wonderful Mac mini that is fast, and it has a Thunderbolt port.

    My hope is to build a pair of DAS that can be built into a rack mounted case, and connected directly to the Mac mini via a Thunderbolt port accessory.

    With that, I thought of two different ways I could add lots of storage:

    1. Lacie eSATA Hub - - It uses the Thunderbolt port to allow two eSATA connections to your Mac. It does *not* support port multiplication. I don't know enough about eSATA, etc, to know what this is exactly capable of. I believe that the only way to have multiple disks present themselves to the eSATA hub as a single disk is if they are in a RAID. So my belief was that I could simply buy a case, put in X number of disks, and utilize a RAID card to allow them to present themselves as a single eSATA drive. However, I can't imagine how this would work because I would believe that a RAID card would need to be connected to a motherboard, or somehow else powered, and that seems like it could get very difficult very quickly. Furthermore, the case would need a power supply for the disks, and I can't imagine that the power supply would work without a motherboard. ?

    I have seen pre-built solutions, for example, this one from OWC: ( ) It has a built in port multiplier, eSATA, and 12TB is $1200. And in essence, this is what I'm looking to build, a self-contained RAID storage device that presents itself as a single eSATA device. But this device is cheap, and that worries me. A comparable solution is offered from SonnetTech ( ), and is $2000.

    With that pre-built device, I could get 2 x 12TB units for $2400, plus the Lacie eSATA hub for $200, totalling $2600 for 24TB of rack-mounted storage.

    Can it be done cheaper?

    2. My other thought utilizes a Thunderbolt accessory from SonnetTech. They make something called the Echo Express PCIe Expansion Chassis, which allows you to use PCIe cards in a small box that is connected to your computer via Thunderbolt. ( ) This is more expensive than the Lacie hub, at $600 or $800 for 1 or 2 slots, respectively. With this device, I could add a RAID card (expensive?) or a card with multiple eSATA ports.

    My thought was that I could buy a rackmount server case, put the disks in, and wire them to the RAID controller card, and I'd actually just leave this SonnetTech box in the server chassis (with no motherboard, seems like there'd be a lot of room), and then it would be a single Thunderbolt cable running from the Mac mini to the rackmount chassis, and that would give me all the storage space I need. This still doesn't alleviate the problem of the hard disks needing a power supply.


    Does anything like either of my two ideas seem feasible? Basically I'm looking to build a couple of rack mounted chassises that can be hooked up via either RAID or eSATA to a Thunderbolt accessory. :)
  2. Lance-AR macrumors 6502

    May 7, 2012
    Little Rock, AR
    I had similar concerns and wound up with a Promise Pegasus R6. I didn't need the speed of TB but needed more open files at once than my Time Capsule was capable of sustaining. Ultimately I didn't feel comfortable with another NAS solution and wanted the simplicity of DAS without the worry of a socket timing out over the network.

    As I now need an offsite backup to compliment the DAS, I wish you the best of luck and look forward to seeing your ultimate solution.
  3. radiogoober thread starter macrumors 6502a

    Jun 7, 2011
    Are you pretty happy with the Promise? It looks like a fantastic unit.
  4. theSeb macrumors 604


    Aug 10, 2010
    Poole, England
    Your ideas are pretty sound, but once you're start building this, I think you'll find the cost and time could add up quite quickly.

    If I were in your position, then I would get something like a Stardom SohoRAID SR4-WBS3 (x 2)

    It's a 4 drive chassis, can be bought without the HDDs and it has hardware RAID 5 with eSATA, USB3.0 & FW800 connectivity.

    Personally I've gone with the Promise Pegasus R4 and it should be arriving tomorrow. I already own a Synology NAS with 5x2TB in RAID 5. I'll be using the Pegasus as a DAS and the Synology will be used to back it up and it also serves media around my house.
  5. Lance-AR macrumors 6502

    May 7, 2012
    Little Rock, AR
    I am very happy with the Promise unit. I believe TB is a positive step in the right direction and am happy with the purchase. The software to manage it wasn't immediately clear to me how to get it set up the way I wanted but I was able to get it into a RAID6 with two redundant drives on the first attempt. It was a nice surprise to find out it was usable during the initial overnight synchronization. I haven't figured out if I need to leave the Pegasus Utility open all the time though or if it keeps a daemon running in the background to monitor everything.

    My biggest concern is hanging the PR6 off a chain of two Thunderbolt Displays. Sometimes my second monitor goes dark for a second and the audio output on the first is always garbled. I had to move my USB keyboard off of the TBD and connect it directly to the Mini as it was unusable when in the TB chain due to high latency with key presses and key let ups not always registering. I haven't done extensive testing but my gut feel is that two TBDs and a PR6 are constrained when sharing the same TB chain.

    On the long term I'm waiting for a Pro with TB support but in the near term I'm hoping the new Minis will have two TB ports. I think the current problems I am experiencing are due to needing more computer than what the mini can handle. Although I suppose on paper, I'm not sure where the constraint would be with the existing Mini other than possibly the TB bus.

    Thunderbolt is very good. Though the promise of many devices in a chain may be wishful thinking in the real world.
  6. jayhawk11 macrumors 6502a


    Oct 19, 2007
    Why don't you step up to something more designed for this? It feels like you're trying to shoehorn consumer devices into a clearly professional-level scenario.
  7. drsox macrumors 65816


    Apr 29, 2011
    Unless you want more than 100MBps, why not get 2 6 bay NAS units ?
    6x 3TB drives will give you 15TB of storage mirrored to the second unit.
    Wait another year and 4TB drives can be used for expension.
  8. FireWire2, Jul 16, 2012
    Last edited: Apr 14, 2014

    FireWire2 macrumors 6502


    Oct 12, 2008
    You set up this 1U rackmount as stand alone USB3.0 or eSATA RAID, it can set up as 5x drives RAID5; or 4x drives RAID5 + Hot spare (more reliable)
    with LCD control:

    this approach will work with Lacie eSATA hub, you can have up to 16TB RAID5 per rack

Share This Page