Context: I am about to invest in my first VSL library; either SE1plus or a Cube licence transfer if I can find a seller, along with Pro Player II. I'm questionning how I can best optimise my new MBP. Having read of the supposed advantage of separate drives I intended to use the existing 750gb HD for project storage and writing audio, replace the optical drive with a 128gb SSD for System, Apps and possibly current projects, and buy an external 256gb SSD for VSL and other libraries. 

But Sound-On-Sound tech editor Hugh Robjohns claims SSD's negate the advantage of separate drives - see quote below. If this is true I would prefer not to carry an external drive around. I would appreciate opinions and advice, thanks!

(Quoted from http://www.soundonsound....acMus&Number=1037827)

"The old-school advice about using a separate audio drive from the system drive is based on the fact that using a single drive for both audio and program data is inherently slow. The reason is that audio data is likely to be in a physically separate part of the drive from the program data, and so the heads will have constantly to move between the two areas on the disk platters as the program seeks instruction data and the audio is being written and replayed. Moving heads across the platters is a relatively slow thing to do. 

Consequently, there was often a speed advantage if the bulky audio data could be written/read from a separate drive in contiguous blocks which is quick to do, while the OS drive is left free to read the program data (and access the virtual scratch memory if necessary) separately where it will also be in contiguous blocks and thus quick and easy to access. The scheme thereby avoids lots of massive head shuffling, and is therefore quicker. 

However, in your case, SSD drives don't have heads or platters to move about. There is no mechanical shuffling, just virtual memory addresses which are vastly faster to access than the equivalent hard drive locations. 

Therefore I would not anticipate any performance difference between using one drive for both audio and OS, or using two separate drives." 

How are you going to connect your SSD for VSL ?

128gb SSD for System, you do not gain much just loading your DAW much quicker

The sound-on-sound tech editor has a point, but there are other things to consider as well.

1) Maximum throughput of the interface between the processor and the "disc" : with multiple discs, potentially using different types of interfaces, the maximum throughput can be a lot higher then a single disc.

( there's currently no single SSD capable of using the full bandwith of thunderbolt / PCI or similar, let alone the full bandwith provided by the I/O chips on the motherboard)

2) SSD's that are re-written a lot, add internal copy/write overhead ( the so called write multiplication factor)

So basically, if you want to keep your library-discs as fast as possible, don't use them to write things on on a regular base ...

Also : don't put the VSL time stretch Cache on your library discs !

What is important is having a fast disc for (system) caches and stuff like that (R/W), for audio (R/W) , and for sample libraries (Read only).

I don't mind waiting a bit for an application or the OS to start, so if it would be just for that, I wouldn't need an SSD (that's a personal thing though, some people want a PC to start up as fast as possible).

However, for pragmatic reasons OS / applications / caches normally reside on the same disc, so if you can afford it, you'll still want this disc to be an SSD too.

Audio : If on the same disc as the OS/app/caches an SSD is must. If not : depends on number of tracks / sample rate. 

Sample Libraries : definitely SSD ! Don't put it on the same disc as the audio : the two BIG data streams (audio / samples) will go to the same disc , on top of that the "write multiplication factor" start playing a role if you write a lot of audio

Conclusion

If you can afford a fast external "disc" , do so.

Prefarably Thunderbolt (fastest AND more stable - less hickups - then USB 3.0) or SAS ($$), or USB 3.0 / dual eSATA.

You can choose to put audio or samples on the external disc, depends on your particular workflow / mobility demands.

- If you have really big / multiple sample libraries, it makes sense to take an enclosure that supports multiple SSD's in a RAID configuration.

(I assume we want to stick  with the "reasonably priced" stuff, muldi-disc multi(parallel)interface enclosure are out of scope)

- If you want to be able to do audio work on the road without an extra additional enclosure, it makes sense to put the audio disc internally

- If you want to "share" (physically de/reconnect) the project/audio disc with others / or with other systems , it makes sense to put the audio disc in the external enclosure.

Looking forward to hear about your future "acquisitions" !

PS : I don't know what kind of MBpro you have, but make sure the throughput in the optical bay slot is high enough ( I believe the current models have equal characteristics for main bay / optical bay).

Most instructive, thanks!