SSD/HDD/Scratch setup MBP

[garstudios]

I got a new 15" 2012 non-retina MBP and im trying to get an SSD and datadoubler/optibay ordered so i can drop it in with my 750GB spinner drive, plus ill be upping the ram to 16gb. Of course the process turns into a major research study in which ive wasted about 2 weeks of my life and burned my eyes out with non-stop reading of all the online back and forth, which has changed my mind all the way back to the beginning. anyways, i got a question, maybe a couple. i figured it would be better asked here among the photographers.

This will be the first ssd in a MBP for me, however i have a few running in some PCs, but i dont use those for photoshop. My previous setups for my MBPs have always been dual 500GB 7200RPM drives. one of which was OS, data, current working photos, the other was just used as a scratch disk (and an occasional major file dump area).

Anywho, this was my thought...

SSD= OS X Lion, Applications, and Scratch and would be 256-512GB

HDD= User folder/data

Concerns

-Scratch sharing drive with OS screwing stuff up. i read a lot of things saying it doesnt matter anymore about keeping them separate.

-User folder on separate drive from OS screwing stuff up.

In the past everyone said that using an external spinning drive via USB for a scratch disk was pointless, however using a 7200rpm external via FW800 was acceptable. Which is what i was doing on the first MBP they released.

-Would using a USB 3.0 external SSD for a scratch disk be acceptable then?

If it is acceptable, would using that external when im at home editing on my desk (which is usually where i edit the large files) for the scratch rather than using the OS ssd be better for my OS ssd? What about occasional use of the OS ssd for the scratch, but major work used with the external?

im just worried about the idea of the scratch sharing a drive with the os.

anyways, thanks

 

[steveash]

There will be people who know far more about this than me but...

I run my MBP from a 96GB SSD for OS and apps and as the primary scratch disk. I have a second internal 7200rpm drive for files and secondary scratch. This works without problems but once I get below 100% efficiency and the scratch disk is being used things slow down considerably. I don't know why this is but it seems more noticeable than previous macs I have used. Saving large files in particular seems to take a long time. Perhaps I have just got used to the zippy speed when it is running from memory. I have been thinking about swapping the files drive for an SSD to see if it improves.

 

[mulo]

I have done almost the exact same as you intend to do, but i located my scratch disk on the HDD.

Slow you think? no.. the user folder has so little activity that it doesn't disrupt scratching much. I have no problems reaching 100MB/s on my HDD, that same HDD only managed 25-30MB/s when i had the OS and apps on it as well.

it is all those little reads and writes of system and app files that ruin a HDDs performance, as it has to move the head around.

 

[Laird Knox]

Also keep in mind that 16GB of RAM will minimize your scratch disk usage. Unless you are running a multitude of apps while working on 24 foot, 300 dpi image.

 

[Ruahrc]

Scratch on the SSD is the way to go. As others have mentioned, what made using the scratch disk so slow was not really the transfer rates, but the seek times. This large speed penalty became doubly slow when the HDD had to cover double-duty for file access both for the OS and the scratch operations at the same time. That is why it was always recommended to have OS and scratch on separate platter drives.

With SSD seek times being orders of magnitude faster (like 1000 times faster) than platter drives, this issue has essentially become moot. It also helps that the SSD usually has superior transfer rates too.

Regarding increased wear on the SSD because you use it as a scratch, personally I feel that by the time you have actually worn out the SSD from too many write operations, the drive will be long obsolete anyway. If you are an extremely heavy user of scratch disk, maybe getting a dedicated drive or a server-class SSD designed for high I/O loads would be prudent- but with relatively large amounts of available RAM nowadays, real-world cases where scratch disk usage is invoked are becoming increasingly rare.