How can I best use an SSD?

Solution 1:

If your main goal is to improve the performance of Photoshop and Lightroom I would focus on these specific applications. Put Photoshop files and the Lightroom lib, Photoshop and Lightroom swap/temp/history files and the Photoshop & Lightroom apps themselves on the SSD.

Moving the system swap file to the SSD will only help if memory used by Photoshop or Lightroom is overflowed to the swap file. But if this is the case extra RAM would improve their performance a lot more.

Moving anything else then the files directly used by Photoshop & Lightroom might result in a faster overall system, but will likely only marginally help improve the Photoshop & Lightroom experience.

Solution 2:

Why not run fs_usage for a while on your mac - you can filter out all the fast IO operations and start to get a feel for which files are coming back slow.

You might find some things you can move - so rather than guessing what might be fast, take some measurements and then only move things that in reality are slow for your specific system?

Solution 3:

HFS+ journal on a different volume

A feature originally intended for Server, but possible with non-Server versions of the operating system. Mac OS X Server v10.6: Moving an HFS+ Journal to a different volume discusses using a partition of (for example) an SSD for the journal for some other volume.

… Journaled HFS+ file systems can benefit from placing the journal on either a separate disk, or on a smaller, faster device. …

Apple's published diskutil(8) Mac OS X Manual Page is not yet updated for 10.7 so if you use Lion, pay attention to the local man page — the section for the moveJournal verb is different.

Whichever manual you follow: if you move a journal, proceed with caution! If the command is not well constructed, the effect can be unexpectedly destructive (I have made such mistakes).

I have not experimented enough to estimate whether moving the journal for a JHFS+ volume could be beneficial to opening poster richardtallent.

External journal on the same physical disk

For some time I had the Apple_Journal type partition for a Core Storage-encrypted Time Machine backup volume on the same disk as that backup volume. After accidentally disconnecting the FireWire cable I had a devil of a job repairing volume structures (details of which are off-topic). I don't know whether having the external journal on the same physical disk was contributory to that devilishness.

If considering an external journal, it may be saner to have the journal on a separate physical disk/device.

Journal for the startup volume

Whilst the manual pages do not explicitly warn against using an external journal for a startup volume, results from my early experiments suggest that doing so may be not a sane move.