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Daisy chain hard drives, combo of USB and firewire

N

NateP

macrumors member
Original poster
Sep 20, 2005
40
0
My time machine drive conked out this morning, so I need to get a new drive, and I am planning on either a Western Digital MyBook or an OWC of some sort. (Any thoughts?)

So here's what I'd like to do. Once I get the backup running again, I'm interested in running a RAID 1 with two external drives. But the catch is this---I have a late model MacBook, so I've only got two USB 2.0 ports.

Here's what I'd like to know. Is it possible to chain things together this way:

MacBook <--USB-- First HDD <--FW-- Second HDD

That is, connect the first drive to the computer via USB (the only option) and the second to the first HDD via firewire.

Has anyone ever tried this?
Any thoughts between the two drive manufacturers above?
 
Any good enclosures or hard drives to suggest, then?
 
What you're planning is software RAID1 on 2 external drives. Not a good idea, as the same data would be written twice onto the bus. For USB, I suspect this will choke the bus.

What you need is a hardware RAID1 enclosure. Your computer will see a single harddrive, so data will only need to be written once onto the bus. Google for "USB RAID1" or something like that. I'm sure you'll find many choices.

Personally, I'm using the OWC Guardian Maximus, which can work off either USB or FW. I do recommend it, even if it's a bit pricey.
 
Is the RAID overkill?

My normal backup solution is to use an external drive for Time Machine backups, Mozy online for an internet backup of my user directory, and the occasional (although not super often) clone of the internal HDD using CarbonCopyCloner. There's also a copy of my docs folder to MobileMe.

I know I don't NEED RAID 1. But is my backup sufficient for most intents and purposes?

BTW, I'm an academic, in case that helps.
 
NateP said:
My time machine drive conked out this morning, so I need to get a new drive, and I am planning on either a Western Digital MyBook or an OWC of some sort. (Any thoughts?)

So here's what I'd like to do. Once I get the backup running again, I'm interested in running a RAID 1 with two external drives. But the catch is this---I have a late model MacBook, so I've only got two USB 2.0 ports.

Here's what I'd like to know. Is it possible to chain things together this way:

MacBook <--USB-- First HDD <--FW-- Second HDD

That is, connect the first drive to the computer via USB (the only option) and the second to the first HDD via firewire.

Has anyone ever tried this?
Any thoughts between the two drive manufacturers above?
Click to expand...

First, USB uses the "tree" topology; the lack of a sophisticated processor means that a peripheral has to be "slaved" to another processor; therefore it must have a host; thus, it -theoretically cannot be daisy chained.

Firewire, however, uses the "daisy chain" topology... which means that both sides of a transfer are "intelligent"; they are not "slaved" to a host. Thus, it is only logical to use this topology for you:

MacBook<--FW-- Second HDD<--USB-- First HDD

Unfortunately you cannot, as you have stated that you have a late-2008 model...


Just out of curiosity, why does it have to be a FW drive?

My first suggestion is to put the second HDD into a USB enclosure, then connect them to a hub and RAID them...
Second is a Dual Hard Drive Enclosure.
 
NateP said:
Is the RAID overkill?

My normal backup solution is to use an external drive for Time Machine backups, Mozy online for an internet backup of my user directory, and the occasional (although not super often) clone of the internal HDD using CarbonCopyCloner. There's also a copy of my docs folder to MobileMe.

I know I don't NEED RAID 1. But is my backup sufficient for most intents and purposes?

BTW, I'm an academic, in case that helps.
Click to expand...

RAID is not an overkill, if you accept that harddrive failure rate is not negligible, AND you want expediency in your recovery. That is critical for production environment, but I'm not so sure it's true for home environments.

I think your setup is already excellent. To me, the key thing is your spare clone and Mozy. If your external HD fails, then quickly update your clone to have a spare copy. Similarly, if your internal HD fails, you can use another machine to clone the external HD. That achieves almost the same effect as RAID1, although there is a short period of uncertainty here when you're performing the cloning. All the while, your precious personal data is backed-up off-site at Mozy. So if you can live with that period of uncertainty, you're fine.
 
superwoman said:
This does not even make sense. You can't dasily-chain USB onto FW.
Click to expand...

No, in that case it's not daisy-chaining a USB drive with a FW- drive. The USB at the end is connected as a peripheral to the FW HD. so in some sense it's more like:

Computer 1 <-FW->Computer2<-USB HD

'cept that Computer 2 is not a computer but a HD. (FW devices are "intelligent")
 
Wikinerd said:
No, in that case it's not daisy-chaining a USB drive with a FW- drive. The USB at the end is connected as a peripheral to the FW HD. so in some sense it's more like:

Computer 1 <-FW->Computer2<-USB HD

'cept that Computer 2 is not a computer but a HD. (FW devices are "intelligent")
Click to expand...

'cept that FW devices are not "intelligent" enough to be a USB host controller. Hub yes, host no. Dude, you've got some serious misunderstandings of how FW and USB work.
 
I would expect that the drives that have both firewire and USB are set up in the firmware so that only one interface can be in use at a time anyway. The USB port isn't intended to work as a host - only as a slave.
 
the ONLY way i see this working is if the first hard drive was a dual type hard drive with BOTH firewire and USB. thus making it both a FireWire connector and a USB hub.


computer<FW>connected to <hard drive>(via firewire)<USB>connected to <2nd hard drive>(via USB)
 
DoFoT9 said:
the ONLY way i see this working is if the first hard drive was a dual type hard drive with BOTH firewire and USB. thus making it both a FireWire connector and a USB hub.


computer<FW>connected to <hard drive>(via firewire)<USB>connected to <2nd hard drive>(via USB)
Click to expand...

Most FireWire drives are set up for daisy chaining, but I've never seen a USB drive, even dual-interface, set up this way. Even if it were, you wouldn't be able to mix interfaces. USB hub, all well and good, but it would need to be connected to the computer by USB.
 
BlueRevolution said:
Most FireWire drives are set up for daisy chaining, but I've never seen a USB drive, even dual-interface, set up this way. Even if it were, you wouldn't be able to mix interfaces.
Click to expand...

yes i know, and im aware you cant mix interfaces. my method doesnt mix interfaces- in that sense anways.

it simply utilises a device (hard drive 1) that has dual interface, which is connected to the mac with both FW & USB at the same time.. this should enable another USB HD to be connected.

i have a setup that is capable of doing this at home, but i use firewire (clearly). i shall check it once the authorities give me back my hard drive case.
 
DoFoT9 said:
the ONLY way i see this working is if the first hard drive was a dual type hard drive with BOTH firewire and USB. thus making it both a FireWire connector and a USB hub.


computer<FW>connected to <hard drive>(via firewire)<USB>connected to <2nd hard drive>(via USB)
Click to expand...

Just because a drive has dual interfaces doesn't mean it can function as a hub. And I don't think hub is the right word; The computer is master, the usb devices are slaves.
 
BlueRevolution said:
Then why not just connect the second hard drive directly to the computer, or via a USB hub? I fail to see what purpose this would serve...
Click to expand...

yes i dont see the purpose either.....the only way i can see it being useful is if you need an extra USB hub (my drive has 3 usb ports), so maybe it would expand that....

old-wiz said:
Just because a drive has dual interfaces doesn't mean it can function as a hub. And I don't think hub is the right word; The computer is master, the usb devices are slaves.
Click to expand...

no it doesnt, but it does mean that both interfaces can function at the same time, meaning that it is possible to use utilise them both. my device is a USB hub, you can connect other devices to it.. whether or not those devices can be smart devices im not sure, but its there! haha
 
If it's of any use to anybody, I ran the Firewire-USB test - and it didn't work.
Scenario:
Item 1 - Pioneer optical drive with audio CD, connected by firewire cable to ...
Item 2 - Seagate external combo f/w-usb hard drive, connected by USB cable to ...
Item 3 - eMac.

I then unplugged the f/w cable from 1 to 2 and replugged it directly to the eMac, all good, audio disk mounted. The ehd then immediately mounted to the eMac desktop, whereas previously it had not.

Ran the test a second time. The audio cd still did not mount when plugged through the ehd via f/w, but this time the ehd did mount via usb (a slightly different switching sequence).

The conclusion is that even though the external enclosure is a combo f/w-usb unit, the two technologies are not compatible for daisy-chain connection to a Mac.
 
Your problems started when you bought the macbook without a firewire port. If everyone boycotted the product, maybe apple would give us back the firewire on the next model.
 
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