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Daisy Chaining External Hard Drives

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interlaced

macrumors 6502a
Original poster
Nov 16, 2005
564
2
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?
 
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.
 
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:
 
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.

pinkartstudent said:
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:
Click to expand...
 
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
 
pinkartstudent said:
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?
Click to expand...

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.
 
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! :)
 
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.

USB can't* do this, Firewire can.
Click to expand...
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.
 
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.
 
sickmacdoc said:
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.
Click to expand...

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

sickmacdoc said:
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.
Click to expand...

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.
 
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?
 
armatt said:
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?
Click to expand...

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.
 
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?

Example:
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.
 
modernmagic said:
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?

Example:
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.
Click to expand...

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.
 
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!
 
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.
 
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?
 
evilcat said:
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.
Click to expand...

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.

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?
Click to expand...

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.
 
itickings said:
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.
Click to expand...

I'm interested, since I couldn't think of when this would happen...Under what conditions would the USB2 solution be better?
 
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?
 
lwien said:
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?
Click to expand...
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.​

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?
Click to expand...
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.​
 
spinnerlys said:
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.​
Click to expand...


But what if I needed to use both drives as a backup, that is, I need to back up 500gb to two 250gb drives?​
 
lwien said:
But what if I needed to use both drives as a backup, that is, I need to back up 500gb to two 250gb drives?
Click to expand...

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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