4 Single-Drive Enclosures vs. 1 Multi-Drive Enclosure

[tray]

Hey all,

I would like to seek your advice on the above.

Scenario 1:
I daisy-chain 4 1-Drive FireWire400 enclosures. I can only use FireWire400 as that is the only option available on my 20’ iMac. USB2 as I have learnt is a poorer alternative. As I foresee that I would be transferring files often between these external drives, I wish that file transfer speeds between these enclosures would be fast.

I have read that FireWire communicates via node-to-node. Therefore, in a daisy-chain of the 4 drives. If I were to transfer a 1GB file from one external drive to the other, it would enjoy the theoretical 400mbps?

Scenario 2:
I purchase a single 4-Drive enclosure that has 4 bays in which I slot my HDD in.The drives could be SATA/PATA but it does not matter since the bottleneck is the FW400 speed right?

This enclosure is connected to my Mac via a single FW400 cable. Suppose I transfer a 1GB file in the aforementioned scenario, between drive to drive. Does the node-to-node principle still apply? That is, is the file is transferred directly from drive to drive? Or, is it transferred first to the internal hard disk drive on the iMac?

If so, would that mean that the file transfer speed would be slower since it involves simultaneously reading/writing from the iMac which would theoretically halve the transfer speed to 240mbps?

I could be uttering nonsense; if so, I do seek your clarification. Thanks!

 

[boneca]

Can you post links to the drives you talking about?

 

[Keebler]

Tray,

imho, the single enclosure with multiple HDs is the way to go. i'm not sure i understand the concern for transferring large files at once. you can just save the files right to the externals?

in terms of cost, internal HDs are dirt cheap these days. much cheaper on a 1:1 basis (1 external 500 vs 1 internal 500 GB drives). the storage towers are cost effective too. and if you get a swappable system, you can add more HDs as you need..therefore increasing your expandability.

i have an external enclosure (it's esata though). not swappable...kind of wish I did that, but still beats having all my externals...which i still use on 1 system.

addonics.com is where i found my enclosure.

good luck,
Keebler

 

[RedTomato]

all in one tower is tidy and cheap I agree.

But as CanadaRam, I think it was, said to me, it presents a single point of failure. Having 4 external drives, each with its own power supply, gives (slightly) greater redundancy.

Personally, I'd still go for the all in one tower. Have you thought about RAIDing them? Raid level 5 would be suitable for 4+ drives.

 

[blodwyn]

Does the node-to-node principle still apply? That is, is the file is transferred directly from drive to drive? Or, is it transferred first to the internal hard disk drive on the iMac?

If so, would that mean that the file transfer speed would be slower since it involves simultaneously reading/writing from the iMac which would theoretically halve the transfer speed to 240mbps?
!

In a file transfer, the data is not necessarily copied to the iMac internal hard disk, but the data from the source drive will travel up the firewire cable into the memory of the iMac, and then get written out to the destination drive. I'm not aware of any way the data could be written straight from one disk to another without the iMac doing the read/write.

This means you have two transfers for every block of data, read from the source, and then write to the destination. If all the drives are on the same firewire cable then you would halve the theoretical maximum transfer speed.

 

[tray]

Any help would be appreciated. Thanks!

 

[livingfortoday]

Personally, I'd still go for the all in one tower. Have you thought about RAIDing them? Raid level 5 would be suitable for 4+ drives.

Ah, if only OS X had software RAID 5 capabilities...

 

[solvs]

I have one of these and it's ok. Not as fast as my internal disk, but no fw drive is. Works fine with my iMac, and it's pretty quiet.

 

[tray]

Can you post links to the drives you talking about?

This is one of those multi-bay enclosures I am considering,

http://www.cfienclosure.com/4044U.html

This is the USB2 version, but there exists a FW version.

 

[tray]

all in one tower is tidy and cheap I agree.

But as CanadaRam, I think it was, said to me, it presents a single point of failure. Having 4 external drives, each with its own power supply, gives (slightly) greater redundancy.

Personally, I'd still go for the all in one tower. Have you thought about RAIDing them? Raid level 5 would be suitable for 4+ drives.

When I have the money, I would definitely go for a RAID enclosure or set up a PC to house all the HDDs. As of now, I can just go for a basic enclosure.

Perhaps, I will use simple software like ChronoSync to maintain copies of my each drive, something like the mirroring of RAID1.

Haha, you left me with a tough decision. I like the redundancy but most of you guys prefer a single tower.

 

[tray]

Just to add, the price of either solution is the same.

 

[tray]

I have one of these and it's ok. Not as fast as my internal disk, but no fw drive is. Works fine with my iMac, and it's pretty quiet.

Do you have any experience with my above question? For example, when you transfer a file from one of your external drive to the other, at what speed does it transfer at?

 

[tray]

In a file transfer, the data is not necessarily copied to the iMac internal hard disk, but the data from the source drive will travel up the firewire cable into the memory of the iMac, and then get written out to the destination drive. I'm not aware of any way the data could be written straight from one disk to another without the iMac doing the read/write.

This means you have two transfers for every block of data, read from the source, and then write to the destination. If all the drives are on the same firewire cable then you would halve the theoretical maximum transfer speed.

By inference, does that mean a file transfer between two external drives in a 4-bay enclosure connected to my iMac via a FW400 cable would have a speed of ~240mbps?

 

[solvs]

Do you have any experience with my above question? For example, when you transfer a file from one of your external drive to the other, at what speed does it transfer at?

Never measured it before, and I don't have it on right now (in the middle of upgrading my drives). Dunno, firewire speeds. You don't get anywhere near the theoretical max of 400Mbps (you won't with anything), but I've transferred several gigs at a time in just a few minutes. Smaller files are almost instantaneous. A little slower from one fw drive to the other than from the internal to the externals, but not too bad. Not a huge performance hit. Works ok for dv video either way.

The 4 bay enclosure has 2 bridges with 2 IDE connectors, so you're daisy chaining anyway if you want to use more than 2 drives, but the solution was cheaper for me and more convenient, speed being the same as it was when I had 2 external fw drives daisy chained.

 

[RedTomato]

Put iMac internal drive into external enclosure?

According to

http://www.welovemacs.com/ihaimg5whtyo.html

you have SATA drives in your iMac. I would check before accepting what the site says.

You could possibly buy a 4 bay SATA enclosure, like

http://www.cfienclosure.com/4043PM.html this has no raid, more likely to work with your iMac.

or

http://www.cfienclosure.com/4043XR.html this has raid, which is cooler, but almost certainly more of a headache to actually make work.

Put your iMac drive in one of the bays, and take a SATA lead out from your internal drive bay out through the iMac case to the external enclosure.

The benefit of this is very high speed SATA drives, and all four drives going at once probably won't be able to max out the SATA II connection.

Max SATA cable length is 1 meter, so you have a little room to play with. You would need a cable with internal connection on one end, and external connection on the other, but they're quite cheap.

As the non-raid enclosure presents each drive as an independent drive, just putting your internal drive in it (or doing a full mirror) should work out of the box with no tweaking.


Guys, what do you think?

 

[tray]

According to

http://www.welovemacs.com/ihaimg5whtyo.html

you have SATA drives in your iMac. I would check before accepting what the site says.

You could possibly buy a 4 bay SATA enclosure, like

http://www.cfienclosure.com/4043PM.html this has no raid, more likely to work with your iMac.

or

http://www.cfienclosure.com/4043XR.html this has raid, which is cooler, but almost certainly more of a headache to actually make work.

Put your iMac drive in one of the bays, and take a SATA lead out from your internal drive bay out through the iMac case to the external enclosure.

The benefit of this is very high speed SATA drives, and all four drives going at once probably won't be able to max out the SATA II connection.

Max SATA cable length is 1 meter, so you have a little room to play with. You would need a cable with internal connection on one end, and external connection on the other, but they're quite cheap.

As the non-raid enclosure presents each drive as an independent drive, just putting your internal drive in it (or doing a full mirror) should work out of the box with no tweaking.


Guys, what do you think?

Yes, the above option is much faster and I could simply get SATA enclosures.

However, how am I to open up my iMac and permanently have an eSATA cable coming out?

I mean, this voids the warranty right?

 

[RedTomato]

Yes, the above option is much faster and I could simply get SATA enclosures.

However, how am I to open up my iMac and permanently have an eSATA cable coming out?

I mean, this voids the warranty right?

You mean like this?

Nah, not at all

 

[livingfortoday]

I actually don't think that should be too difficult. In fact, I'm pretty sure the SATA cable is easily accessible once you open up the case, since it hooks up to the side of the logic board facing the back:
http://mactree.sannet.ne.jp/~kodawarisan/imac_intel/01141052.jpg

Not too bad of an idea to try that, though I personally would just go with a FW solution.

 

[blodwyn]

By inference, does that mean a file transfer between two external drives in a 4-bay enclosure connected to my iMac via a FW400 cable would have a speed of ~240mbps?

USB2 is 480mbps - FW400 is 400mbps so halving it would be 200mbps. This is a theoretical maximum. Other factors play into it, like the disk buffer size, whether the file is contiguous or fragmented and therefore the seek time of the heads, speed of the disk rotation, position of the file on the disk (close to the edge or the middle). All these affect the rate at which data comes off the disk, and therefore onto the FW bus.