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editor0400
Apr 23, 2013, 11:54 AM
I just purchased a refurbished white iMac 2.0Ghz (iMac 5,1) to make use of my Logic Pro and Pro Tools licenses.

Reason being, Logic 8 won't install on my MacBookPro with Retina Display. Despite being a Universal App, the installer is PowerPC only, and thus won't install on Mountain Lion. Pro Tools 8 was never certified for Mountain Lion.

So, rather than to upgrade both Logic and Pro Tools, I bought a refurb computer for $229. It runs awesome, and I thought I may as well put my old FW 400 drives to use.

Situation: I was trying to playback a complex Logic project (approx 30 tracks) and was having CPU load issues. However I don't think the issue was with the CPU specifically, I'm not sure if my FW400 drives (Lacie, 7200 rpm) are fast enough to stream that much audio.

Questions: Is there a way to measure how much data it takes to stream a single track of audio (.wav, 48k, mono) ?. How many tracks are you guys able to playback over Firewire 400?

Further more: Is there an easy way to split up my project media across 2 Firewire400 drives to take advantage of more bandwidth?

I realize in hindsight that the iMac might not have been the best purchase. The CPU is perfectly fine but I forgot the main drawback of these old AIOs is the drive bandwidth with a lone os drive controlling the system!



ChrisA
Apr 24, 2013, 07:30 PM
1) the best why to split your media over two drives is to make a software RAID device. With two drive you "stripe" them. It will look to the OS just like one bigger disk that is faster. Even if you have only one media file it will be distributed over both drives.

The down side is that if either drives fails you loos all data on both drives. so back up everything.

software RAID is easy and does what you want. Hardware raid will have better performance but for audi you don't need such performance. Had you said "30 tracks of HD video" then yes, you'd need some serious performance. But audio is easy

2) It is easy to know the data rates. a 48K 16-bit stereo tracks has 48 x 1024 x 2 x 2 bytes per second of data Lets call it 200,000 bytes per second. 30 such tracks have a total of 6 megabytes per second.

Figure about a 20% "overhead" and you get no more than 8MB/sec

Try running Apple's "activity Monitor" and you will get real data on CPU and disk IO. So there is no need to guess when you can measure.

I just purchased a refurbished white iMac 2.0Ghz (iMac 5,1) to make use of my Logic Pro and Pro Tools licenses.

Reason being, Logic 8 won't install on my MacBookPro with Retina Display. Despite being a Universal App, the installer is PowerPC only, and thus won't install on Mountain Lion. Pro Tools 8 was never certified for Mountain Lion.

So, rather than to upgrade both Logic and Pro Tools, I bought a refurb computer for $229. It runs awesome, and I thought I may as well put my old FW 400 drives to use.

Situation: I was trying to playback a complex Logic project (approx 30 tracks) and was having CPU load issues. However I don't think the issue was with the CPU specifically, I'm not sure if my FW400 drives (Lacie, 7200 rpm) are fast enough to stream that much audio.

Questions: Is there a way to measure how much data it takes to stream a single track of audio (.wav, 48k, mono) ?. How many tracks are you guys able to playback over Firewire 400?

Further more: Is there an easy way to split up my project media across 2 Firewire400 drives to take advantage of more bandwidth?

I realize in hindsight that the iMac might not have been the best purchase. The CPU is perfectly fine but I forgot the main drawback of these old AIOs is the drive bandwidth with a lone os drive controlling the system!

Johbremat
Apr 27, 2013, 01:28 AM
I'd question the wisdom of software RAID. Most likely it's not the drive speed but the interface over which the data is transferring.

Two FW400 ports will shuttle data across to memory no issue, but surely there'll be a contention strategy managing when reads and writes are occurring. Also, the ports will likely be off the same bus, so software RAID wouldn't yield much of a boost - if any - as you'll saturate the controller.

The other issue is that, like all RAID 0 solutions, the failure of one disk means a complete data loss. I wouldn't recommend any RAID configuration that isn't 0+1, 1+0, 5 or 6 when dealing with creative projects.



If anything, would say that all your project assets go on one disk and your creative output live on the other. Alternatively, have your creative output live on the main drive and if Logic or PT offers the option, set the second external drive as a 'scratch disk' (acts like RAM; volatile, unsaved material is temporarily stored here).



Within Logic and PT, see if a 'freeze' function is available. Under Ableton Live it's possible to freeze tracks - in effect, pre-rendering the tracks - to relieve some of the pressure on the system.



Also, are you using an audio interface? If not, it'd be worth investing in. It'll allow you to offload a good chunk of processing off the CPU.

ChrisA
Apr 27, 2013, 06:08 PM
The interface is NOT the bottle neck. The drives really are much slower than the interface. Striping really does improve speed. And YES you are correct the risk of data loss is 2x greater.

one SATA hard drive might have a sustained speed of about 50+ MB per second and a FW400 cable is nearly eight times faster than that. DOn't look at burst rates across the SATA interface. These are fast but not sustainable over many seconds or minutes.

One would never use a stripped array for long term storage. You'd need Time Machine to copy it to a few different local drives and some kind of off site rotation plan.

If you really need performance you only have two options (1) N-way stripped drives or (2) flash drives.

If you care about the data, the rule is always that you must do ALL of the following
(1) Keep the data on at least three different physical media (RAID counts as ONE media)
(2) Keep the data in at least two different geographical locations.
(3) do the above even while a backup is in process. This likely means four copies as a minimum.

All that said, audio recording does not need a lot of performance. HD video does but audio is easier.