Daisy Chaining External Hard Drives

Discussion in 'Mac Accessories' started by interlaced, Nov 10, 2006.

  1. interlaced macrumors 6502a


    Nov 16, 2005
    Can I "daisy chain" (i think that term is hilarious) two different external hard drives? I've never had experience with connecting two hard drives and I bought a new, bigger one to take the place of the other. However I think I might need both after all. Is it possible to connect a Seagate and LaCie (or any other brand) together and kind of make them act as one so I can also save a port on my macbook pro?
  2. hodgjy macrumors 6502

    Apr 15, 2005
    You can daisy chain the drives together and they will work just fune. They won't "act as one drive" as you say. OS X will recognize them as two completely different drives.

    Also, you have to have the first drive in the chain turned on if you want the second drive to be recognized by OS X.
  3. pinkartstudent macrumors newbie

    Feb 1, 2008
    this is jsut waht i need to do - copy some stuff from my external HD to that of another editor. i have been told i can attach one to another: but how do i physically do this, pleae?

    thanks in anticipation, D:confused:
  4. hodgjy macrumors 6502

    Apr 15, 2005
    Both drives have to be of the same connection type (usb or firewire). Plug the second drive into the available slot on the rear of one of the drives. Most firewire drives have an available slot, but not all usb drives do.

  5. pinkartstudent macrumors newbie

    Feb 1, 2008
    but if i attach the first hd to the mac via firewire that's the port used up, so surely i'd only be left with a usb to usb connection for the second to the frist?

    Sorry to be a pain ... D
  6. itickings macrumors 6502a


    Apr 14, 2007
    The firewire on the computer is used up physically, but if the firewire drive using the port has a second firewire port anything connected to that port will be accessible to the computer too.

    Most firewire drives have two firewire ports. One to connect the drive to the computer, and another one to allow daisy chaining, ie connect an additional firewire unit.

    Typical use:
    Computer <-Firewire-> Drive A <-Firewire-> Drive B (and so on)

    USB can't* do this, Firewire can.

    *) OK, technically a drive could contain a built-in hub, but those are rare.
  7. pinkartstudent macrumors newbie

    Feb 1, 2008
    yes yes yes! connected laptop to my hd using firewire, then connected two hds together using firewire also. all worked fine (although i had to reconenct the media for some reason). thanks folks! :)
  8. loweevan macrumors newbie

    Nov 29, 2008
    I recently bought a new macbook to replace my 4 year old PowerBook G4. It was time for a new one. However, in dropping to the macbook, I've lost the firewire ports that I have used for my two external drives (one solely for backups, the other for large files that I use infrequently).

    One drive is a LaCie with 2 FW800, 1 FW400, and 1 USB port (the square kind one frequently sees used with printers). The other drive is a WD mybook studio with 2 FW800, 1 eSATA, and 1 usb port. Both drives are powered. Previously I had daisy-chained the drives together using FW800, and connected to the computer the same way. Now, when I connect the two together and then run the USB from the WD to my computer, it doesn't recognize the LaCie drive. In fact, it won't recognize the WD unless I unplug the FW from it. After the computer detects it, I can plug the FW back in and it doesn't disturb anything.

    Do you mean that the drives all need to be connected USB <-> USB or FW <-> FW, or that USB simply can't daisy-chain? If USB is able to daisy-chain and the failing of my drives is that there is only one port (thus no port to plug the secondary into the primary), does a powered USB hub slow down connection speeds? I could just connect them both separately if speed isn't inhibited.

    Sorry for the edit. I had missed a post that changed my question.
  9. sickmacdoc macrumors 68020


    Jun 14, 2008
    New Hampshire
    As I understand it you are currently trying to use a chain along the lines of:

    Computer-----USB----->Drive 1------FW------>Drive 2

    The results of this would match your observations. A FireWire cable between Drive 1 and Drive 2 will NOT be recognized. That only works if Drive 1 is connected to the computer via FireWire as well, as you had it before. The Firewire circuitry in the drives is independent of the USB circuitry, so what you are trying to do is impossible since there is no incoming data to the FireWire circuitry in Drive 1 to pass along (daisy chain) to Drive 2.

    In answer to the second part, simply put USB has no daisy chaining ability. That is why there is only one USB on the back of the drives, as a second would be useless. To use multiple USB drives on a system with a single USB port yes you need to use a hub. As long as the powered hub is noted as being USB 2.0 compliant (as to opposed to ancient ones that were only USB 1.1 compliant) there will be no slowdown whatsoever compared to plugging a USB drive directly into the port on the computer.

    USB 2, by it's very design specifications, is somewhat slower than FireWire 400 (and noticeably slower than it was if you were using FW 800 all the way in to the computer before as it appears you were) but there is no way around that.
  10. loweevan macrumors newbie

    Nov 29, 2008
    Thank you. Understanding the circuitry is very helpful. I'm glad to know not only that it won't work, but also why.

    I knew that the speeds would be a lot slower, and I've observed that already. I wish that it wasn't nearly $1,000 more for the mbp, but... so it goes.

    Thanks again for your answer. I really appreciate it.
  11. armatt macrumors newbie

    Aug 31, 2009
    just wondering if (obviously this is theoretical) there is any limit to daisy chaining?

    I use a 1TB Western Digital My Book for freelance filmmaking and am wondering how far ahead in advance i need to plan - ie: bite the bullet and get 2TB/4TB drive now while they're more expensive? or simply get another 1TB because that's all i need for now, knowing that i could daisy chain a third later on.

    does anyone have any experience daisy chaining 3+ externals?
  12. jackerin macrumors 6502a

    Jun 29, 2008
    Try googling for Firewire daisychain limit or something, iirc the limit is at 64 devices...
  13. maghemi macrumors 6502

    Aug 7, 2009
    Melbourne Australia
    I've had 3 daisy chained to each other working fine. However what you have to remember is they're all sharing the same firewire bandwidth. So if you're copying a large file to one of the three drives, and then trying to run things off another drive, they'll be sharing the bandwidth and hence slow down.
  14. modernmagic macrumors member

    Sep 14, 2003
    When you daisy chain firewire drives and copy files from one to another do the files get transferred to the mac and then back to the drives?

    1 gb file on drive A > transferred to macbook
    macbook transferres file to drive B

    I am asking because I have a 400 mhz pismo powerbook running as my backup system. I want to now make a duplicate of the FW drive A, connected to the pismo, onto Drive B and store it offsite. At 400 mhz I would assume the pismo would bottle neck the copying of 2 TB of data and take days.

    If the FW 400 daisy chain was not bottle necked by the pismo then then copying of 2 tb would be much faster.
  15. jpyc7 macrumors 6502

    Mar 8, 2009
    Denver, CO
    I've read on the wikipedia page that Firewire allows peer-to-peer communication which means that the host processor would not be as involved. The interface chip on your powerbook might still be involved depending on whether the electrical connections are direct or not. Anyway, your host processor will still be involved to some extent since I am sure that it gets updates on how far along the copying is.

    However, there shouldn't be a temporary image copy on your macbook hard drive. So your internal HD is not a bottleneck.
  16. modernmagic macrumors member

    Sep 14, 2003
    thanks for the reply.

    Here is my experience:
    Drive A FW400 to 400mhz pismo powerbook
    Drive B USB to 400 mhz pismo
    Estimated copy time 190 hours

    Drive A FW800 to 2.53 ghz macbookpro
    Drive B Daisy chained to Drive A via FW800
    Completed copy in 3 hours.

    I'm still proud of my old Pismo for running as a backup server with CarbonCopy Cloner and Crashplan!
  17. Jaro65 macrumors 68040


    Mar 27, 2009
    Seattle, WA
    I have three HDs daisy-chained using FW800 and it all works great.
  18. pm9448 macrumors newbie

    Mar 21, 2009
    Logical Volume Manager

    I say this with trepidation, but if you want a "single drive" with daisy chained devices, Linux LVM might be right for you. Add as many physical volumes (each USB drive) to the Volume Manager and you can extend or create new logical volumes. If for example, you want to put all your music on /Music partition. You can keep growing that file system for a very long time just by adding new drives to it.

    I am in the market now for media storage and not sure whether something as simple as daisy chaining or something a bit more elaborate like Drobo might be the way to go.
  19. evilcat macrumors member

    Apr 18, 2005
    Just out of interest, since the iMac has only one FW800 port:

    I know USB2 is pig-slow, but which of the following would give the best combined data transfer speed?

    a. 2 FW800 hard drives, daisy-chained and transferring simultaneously
    b. 1 FW800 hard drive and 1 USB2 hard drive

    Presuming they were the same disks (7200RPM), enclosures, etc.

    Also, if I wanted to run an external disk off USB2 using bus power, would it be fast enough to function solely as an iTunes drive? The music is all Apple Lossless but after import would performance really be impacted by the USB bus? And is there any point using a 7200RPM disk in this scenario over a 5400RPM?
  20. itickings macrumors 6502a


    Apr 14, 2007
    There are way too many variables to answer that, I can easily construct real-world situations for both options. Realistically though, two daisy-chained FW800 drives will be better, but as mentioned situations can be constructed where 1xFW800+1xUSB2 would give higher throughput.

    Running on bus power won't make transfers slower per se as opposed to externally powering of the same drive. It is just that bus powered drives in the USB2 world is nearly always 2.5" drives, which in most cases are way slower than 3.5" drives. A 5400rpm 2.5" drive over USB2 will however be much much faster than needed for real-time playback of lossless audio in any case.
  21. Snowbound macrumors regular

    May 19, 2008
    I'm interested, since I couldn't think of when this would happen...Under what conditions would the USB2 solution be better?
  22. lwien macrumors regular

    Jun 19, 2009
    Will SuperDuper and/or TimeMachine recognize 2 daisy chained drives as one and if not, how would it work if I want to create a bootable drive with SuperDuper?

    Also, if one drive has a 16mb cache and another has a 32mb cache, in using the backup programs above, will there be an overall speed drop off due to one of the drives having a smaller cache?
  23. spinnerlys Guest


    Sep 7, 2008
    forlod bygningen
    No, SuperDuper and TimeMachine will see the drives as Mac OS X does, if they show up as two drives in Mac OS X, the same will happen in SD or TM for that matter.
    Choose the correct drive to use as backup HDD. The other HDD will not be affected.​

    I don't know about that, but backing up via SD will not use the maximum transfer speed the port you chose does offer, thus the cache size is rather rather negligible.​
  24. lwien macrumors regular

    Jun 19, 2009

    But what if I needed to use both drives as a backup, that is, I need to back up 500gb to two 250gb drives?​
  25. spinnerlys Guest


    Sep 7, 2008
    forlod bygningen
    Then either split the backup in half and spread it onto the two 250GB HDDs or look if you can make a Firewire RAID out of those two HDDs if they use Firewire, but I vote against the RAID option, as that would be not secure, unless you have another non-RAID backup. What about getting another 500/1000 GB HDD and putting and putting it into another or already existing enclosure?

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