Hence the RAM Disk score was 27X faster.

RAM Disk Test Total 2041.64

———————–Sequential 1288.62
—–Uncached Write 1055.33 647.96 MB/sec [4K blocks]
—–Uncached Write 3243.49 1835.16 MB/sec [256K blocks
-----Uncached Read 634.50 185.69 MB/sec [4K blocks]
—–Uncached Read 3674.15 1846.60 MB/sec [256K blocks]

———————–Random 4912.12
—-Uncached Write 1964.06 207.92 MB/sec [4K blocks]
—-Uncached Write 5929.19 1898.15 MB/sec [256K blocks]
—-Uncached Read 24386.08 172.81 MB/sec [4K blocks]
—-Uncached Read 10471.40 1943.04 MB/sec [256K blocks]

Internal 7200 Disk Test 74.07
Sequential 163.75
Uncached Write 172.35 105.82 MB/sec [4K blocks]
Uncached Write 163.45 92.48 MB/sec [256K blocks]
Uncached Read 131.50 38.48 MB/sec [4K blocks]
Uncached Read 203.98 102.52 MB/sec [256K blocks]
Random 47.86
Uncached Write 15.17 1.61 MB/sec [4K blocks]
Uncached Write 313.67 100.42 MB/sec [256K blocks]
Uncached Read 111.01 0.79 MB/sec [4K blocks]
Uncached Read 182.95 33.95 MB/sec [256K blocks]

I am not sure why a RAM disk appears to improve OS X speed. In theory OS X cache and VM control are so good that RAM disks are unable to increase speed. I did see one post which said RAM disks always use ‘wired’ memory but this fails to explain improvements when memory is little used.

I was able to increase Safari speed without a RAM disk by manually trashing all preferences, history and caches but not bookmarks. ‘Reset Safari’ did not reset all of these. Perhaps examining ALL iTunes files will resolve your issue. Probably best to backup before you start.

The iMac saved RAM disk contents to disk automatically and could be booted from the RAM disk as mentioned elsewhere. It was practical to use both Disk First Aid and Norton Utilities while so booted even if the applications were too large to reside on the RAM disk.

I have a very old web page documenting speeding up Netscape with a RAM disk – http://links.open.ac.uk/www/ns.html

I have just demonstrated that a similar trick with Safari 5 on my 733 MHz G4 with OS X 10.5.8 also results in a speed improvement. This is what I did:

1 – Quit Safari.

2 – Used the terminal command from earlier here:
diskutil erasevolume HFS+ “ramdisk” `hdiutil attach -nomount ram://1165430`

3 – Via the Finder I dragged my Safari folder from /Users/neville/Library/Safari to the RAM disk and kept a backup copy elsewhere.

4 – Created a link via the terminal:
ln -s /Volumes/ramdisk/Safari /Users/neville/Library

5 – Restarted Safari.

Don’t forget to replace ‘neville’ with your user name and make sure that you backup your Safari file as the RAM disk will probably be lost when you shutdown or restart your Mac.

OS X has the facility to store RAM to disk automatically – portables do this to conserve battery and many other Macs can be modified also. I use it several times a day when I put my G4 desktop to sleep (details available if you can contact me!). I think that doing it during normal shutdown is possible but I cannot remember the details. Those interested could try ‘man pmset’ and ‘pmset -g’ in the terminal.