Anyone Have Two Hard Drives in Their iMac?

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ohsnaphappy
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p.1 #1 · Anyone Have Two Hard Drives in Their iMac?

I'm curios to know the transfer rate between two internal hard drives? For example, are you able to transfer data from the internal HDD to the internal SSD faster than from an external Thunderbolt drive to the internal SSD? I would love to know the transfer rate. For example:

Little Big Disk sends 30GB to internal SSD at 200MB/s.

Internal HDD sends 30GB to internal SSD at ?MB/s

Internals are always faster right?

Jan 16, 2013 at 07:49 AM

alexkiowa
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p.1 #2 · Anyone Have Two Hard Drives in Their iMac?

no, internal would not be faster if you are talking about single HDD.
what little big disk do you have? Thunderbolt version? I believe little bit disk would be faster. I have iMac, little big disk, Caldigit VR2, and SSD. VR2 so far performs the best and functions much better than Lacie's.

Jan 16, 2013 at 08:32 AM

k7xd
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p.1 #3 · Anyone Have Two Hard Drives in Their iMac?

ohsnaphappy wrote:

Internals are always faster right?

Internal SATA will always be fastest if they are used right.
For volume workflow this is a basic configuration.
If you are constantly reading and writing to the same drive its obviously going to slow things down.
The worst situation is a single internal drive. Totally buggers up the data flow.

C: Mount your OS and programs. SSD is nice here because it does not need to be big.
D: This will be the drive that you read your data from.
E: The drive you write your processed data to.

Jan 16, 2013 at 08:46 AM

mhayes5254
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p.1 #4 · Anyone Have Two Hard Drives in Their iMac?

I have two (OS and Data) in my Mac Pro, although I never actually measured the speeds.

I have a variation on what k7xd describes (and somewhat contradicts what I said above). OS and LR catalogs/previews are on a PCI card based SSD. RAW files on D:. In a PS type workflow where you are generating new files for output, I would want the originals and processes files in the same place.

Jan 20, 2013 at 07:04 PM

Alan321
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p.1 #5 · Anyone Have Two Hard Drives in Their iMac?

Writing is usually slower than reading.
Data on the outer tracks of a HDD can transfer up to twice as fast as data on the inner tracks.
Some drives are just faster than others.
Apart from USB and perhaps firewire, the data transfers to/from a single physical drive are slower than the drive interface to the outside world could cope with.
To fully utilise a drive interface you need SSDs and/or multiple drives to share the burden.

In the case of internal HDD vs external thunderbolt HDD, the drives will be the limiting factor. Unless the Little big disk is a striped RAID it will be much the same performance as the internal HDD, allowing for where the data is on the drive and whether one drive is superior to the other.

Another factor is whether or not the data is identical from each drive. Fewer, bigger files will transfer faster than many smaller files amounting to the same number of MB.

And it pays to know what other software is doing while you test - e.g. indexing one of the drives or otherwise diverting the heads from where your source data is will slow down the read rate.

Jan 21, 2013 at 10:14 AM

OntheRez
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p.1 #6 · Anyone Have Two Hard Drives in Their iMac?

All things being equal - that is the drives are exactly the same: model, rotation speed, cache, etc. - hard drive thru put speeds in descending order are:

Internal
eSATA
Firewire 800
Firewire 400
USB 2.0

There are other variables like how fragmented and how full a drive is that can effect read/write times, but in general the above list holds true. Given the expense of SSD drives, it makes the best sense to use them as boot/application drives rather than for data.

Thunderbolt and USB 3.0 promise remarkable thru put but I'm unaware of any real world demonstrations of their superiority. The exception to the above list involves data warehouses and server farms with the need to deliver huge quantities of data in real time. They use extremely advanced (read mind-bending expensive) RAID and interconnect systems. You don't even want to think about such systems.

I have 4 internal and 2 external drives in my MacPro. The externals are eSATA and serve as backup devices with one of them dedicated to my photo library. I use a pair of Fujitsu 750GB 7200 RPM, 64MB cache drives as my internal work drives. They store only the photo library. All programs live on the boot drive. I periodically (after backup) copy the current library over the older version. This gives me (1) a fall back copy of my library that while not up to date would survive the other drive's failure and (2) such a large copy operation gives about 85% of the efficacy of a complete reformat in terms of defragmenting the drive and giving quicker drive read/write times. I've never timed how long it takes my now ~300GB library to copy from one drive to the other, but lets just say I go have a cup of coffee while it is going on.

Robert

Jan 22, 2013 at 08:55 PM

ohsnaphappy
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p.1 #7 · Anyone Have Two Hard Drives in Their iMac?

All this information has been awesome! The Mac will be here Thursday, so I'm going to transfer 20GB, or thereabouts, to the ssd from the hdd and visa versa, to see what the transfer rates are. I'm not sure if the internal hdd is 5400 or 7200, but I'll find out when it gets here.

Jan 22, 2013 at 09:18 PM

Bifurcator
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p.1 #8 · Anyone Have Two Hard Drives in Their iMac?

Internal SATA and eSATA will always be identical in speed. The difference in speed between the two will be determined only by the length of the cable you use. And that's almost not measurable in benchmarking apps let alone real-world use.

Thunderbolt should be identical as well - maybe a tad more latency due to the interface and cable length - but again I doubt noticeable.

In OntheRez's list Internal SATA, eSATA, and thunderbolt should be on the same line.

So no, internal is not faster these days than external.

Jan 23, 2013 at 08:55 AM

OntheRez
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p.1 #9 · Anyone Have Two Hard Drives in Their iMac?

Bifurcator wrote:
Internal SATA and eSATA will always be identical in speed. The difference in speed between the two will be determined only by the length of the cable you use. And that's almost not measurable in benchmarking apps let alone real-world use.

Thunderbolt should be identical as well - maybe a tad more latency due to the interface and cable length - but again I doubt noticeable.

In OntheRez's list Internal SATA, eSATA, and thunderbolt should be on the same line.

So no, internal is not faster these days than external.

You're right in noting that internal SATA and eSATA are in theory the same speed. I've noticed somewhat slower (though truthfully not that significant) thru put with eSATA. I think the card and cable come into play here. As for Thunderbolt, could you direct me to some real world testing on it? I've not be paying a lot of attention to the technology as MacPros don't have it and I'll not upgrade until there is a new and better MacPro. (iMacs just don't have the expandability nor raw processing power.) I suppose I could search but if you have a link I'd be interested in reading it.

Thanks,

Robert

Jan 24, 2013 at 02:50 PM

lou f
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p.1 #10 · Anyone Have Two Hard Drives in Their iMac?

OntheRez wrote:
Bifurcator wrote:
Internal SATA and eSATA will always be identical in speed. The difference in speed between the two will be determined only by the length of the cable you use. And that's almost not measurable in benchmarking apps let alone real-world use.

Thunderbolt should be identical as well - maybe a tad more latency due to the interface and cable length - but again I doubt noticeable.

In OntheRez's list Internal SATA, eSATA, and thunderbolt should be on the same line.

So no, internal is not faster these days than external.

You're right in noting that internal SATA and eSATA are in theory the same speed. I've noticed somewhat slower (though truthfully not that significant) thru put with eSATA. I think the card and cable come into play here. As for Thunderbolt, could you direct me to some real world testing on it? I've not be paying a lot of attention to the technology as MacPros don't have it and I'll not upgrade until there is a new and better MacPro. (iMacs just don't have the expandability nor raw processing power.) I suppose I could search but if you have a link I'd be interested in reading it.

Thanks,

Robert

thunderbolt is fast, you can run 2 6g ssd's in raid 0 and still not max it out.

Jan 24, 2013 at 02:56 PM

cgardner
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p.1 #11 · Anyone Have Two Hard Drives in Their iMac?

System performance in general is also affected by the amount of DRAM and virtual memory (VM). In the activity monitor application on a Mac you can see the overall VM page ins / page outs to disk.

In my case I bought one the early Aluminum iMacs with only 2GB of DRAM and the system was continually paging to virtual memory. Upgrading DRAM to 6GB (the max for that model) eliminated most the VM paging and there was a noticeable uptick in performance overall.

Applications like Photoshop use "Scratch Disk" while working on files when the DRAM isn't sufficient. The more DRAM you have the fewer scratch disk swaps there will be. You specify the primary and secondary scratch disks and how much DRAM is reserved for PS in the preferences.

So in addition to disk speed considerations already mentioned you'll want to max. out the DRAM to improve overall performance.

FWIW - Thunderbolt is a welcome addition. The implementation of Firewire 800 on the iMac (at least my model) sucked. Minor glitches will trip a "circuit breaker" on the Firewire bus knocking a drive off line. Resetting it requires disconnecting all externals and power cable for five minutes, rebooting, shutting down, reconnecting and rebooting a second time; a major PITA.

Jan 24, 2013 at 04:16 PM

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