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Pamar Bjornson

Registered User

Join date: 5 Oct 2005

Posts: 67

03-10-2006 01:44

I remember reading someone getting encouraging results on a PC by creating a ramdisk and moving the SL cache on it.

Has anyone tried the same with a Mac?

I am currently at the office, but I'd like to install http://www.donelleschi.com/ramdiskcreator/ and see if there is any improvement (I have the newest PPC iMac 17" with 1.5 Mb).

Has anyone tried this? Worth it? Can anyone tell me the cache file name on MacOS, so that I can just create a symlink to the ramdisk?

TIA...

Argent Stonecutter

Emergency Mustelid

Join date: 20 Sep 2005

Posts: 20,263

03-10-2006 08:57

If you have enough memory for a RAM disk, Mac OS X should already be using any RAM SL isn't already using to cache disk blocks, so you're effectively already using as big a "RAM DISK" cache as you can... for reads from the cache.

Writes to the cache are still limited by the disk speed, but that happens in the background, the app shouldn't be delayed by the write unless you're memory starved and it's waiting on the write to complete before something else it needs can be paged in... and in that case a RAM disk will probably make things worse.

Pamar Bjornson

Registered User

Join date: 5 Oct 2005

Posts: 67

03-10-2006 10:35

From: Argent Stonecutter

If you have enough memory for a RAM disk, Mac OS X should already be using any RAM SL isn't already using to cache disk blocks, so you're effectively already using as big a "RAM DISK" cache as you can... for reads from the cache.

Writes to the cache are still limited by the disk speed, but that happens in the background, the app shouldn't be delayed by the write unless you're memory starved and it's waiting on the write to complete before something else it needs can be paged in... and in that case a RAM disk will probably make things worse.

In thoery I agree, but considering some seem to get much better performance with ram disks on PCs (and windows does bufferize disks reads) I wondered if anyone had tried this on Mac, too.

Ushuaia Tokugawa

Nobody of Consequence

Join date: 22 Mar 2005

Posts: 268

03-10-2006 10:45

You can easily create a ram disk on MacOS X without any third party products. I posted detailed instructions here:

/108/b8/73105/1.html#post759615

I have tried it and didn't notice any increase in performance.

Argent Stonecutter

Emergency Mustelid

Join date: 20 Sep 2005

Posts: 20,263

03-10-2006 13:50

From: Pamar Bjornson

In thoery I agree, but considering some seem to get much better performance with ram disks on PCs (and windows does bufferize disks reads) I wondered if anyone had tried this on Mac, too.

Windows memory management is horrible - even on XP Windows will save data off to the swapfile rather than keep it in memory, and leave memory unused rather than use it for disk cache.

From: Ushuaia Tokugawa

You can easily create a ram disk on MacOS X without any third party products.

that's not really a "ram disk" in the usual sense. The contents of that "ram disk" are paged in and out just like any other disk data, they're just written a bit more efficiently and they're paged to the swapfiles rather than to a directory tree on disk.

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MacOS Ramdisk?

MacOS Ramdisk?
Pamar Bjornson Registered User Join date: 5 Oct 2005 Posts: 67	03-10-2006 01:44 I remember reading someone getting encouraging results on a PC by creating a ramdisk and moving the SL cache on it. Has anyone tried the same with a Mac? I am currently at the office, but I'd like to install http://www.donelleschi.com/ramdiskcreator/ and see if there is any improvement (I have the newest PPC iMac 17" with 1.5 Mb). Has anyone tried this? Worth it? Can anyone tell me the cache file name on MacOS, so that I can just create a symlink to the ramdisk? TIA...
Argent Stonecutter Emergency Mustelid Join date: 20 Sep 2005 Posts: 20,263	03-10-2006 08:57 If you have enough memory for a RAM disk, Mac OS X should already be using any RAM SL isn't already using to cache disk blocks, so you're effectively already using as big a "RAM DISK" cache as you can... for reads from the cache. Writes to the cache are still limited by the disk speed, but that happens in the background, the app shouldn't be delayed by the write unless you're memory starved and it's waiting on the write to complete before something else it needs can be paged in... and in that case a RAM disk will probably make things worse.
Pamar Bjornson Registered User Join date: 5 Oct 2005 Posts: 67	03-10-2006 10:35 From: Argent Stonecutter If you have enough memory for a RAM disk, Mac OS X should already be using any RAM SL isn't already using to cache disk blocks, so you're effectively already using as big a "RAM DISK" cache as you can... for reads from the cache. Writes to the cache are still limited by the disk speed, but that happens in the background, the app shouldn't be delayed by the write unless you're memory starved and it's waiting on the write to complete before something else it needs can be paged in... and in that case a RAM disk will probably make things worse. In thoery I agree, but considering some seem to get much better performance with ram disks on PCs (and windows does bufferize disks reads) I wondered if anyone had tried this on Mac, too.
Ushuaia Tokugawa Nobody of Consequence Join date: 22 Mar 2005 Posts: 268	03-10-2006 10:45 You can easily create a ram disk on MacOS X without any third party products. I posted detailed instructions here: /108/b8/73105/1.html#post759615 I have tried it and didn't notice any increase in performance.
Argent Stonecutter Emergency Mustelid Join date: 20 Sep 2005 Posts: 20,263	03-10-2006 13:50 From: Pamar Bjornson In thoery I agree, but considering some seem to get much better performance with ram disks on PCs (and windows does bufferize disks reads) I wondered if anyone had tried this on Mac, too. Windows memory management is horrible - even on XP Windows will save data off to the swapfile rather than keep it in memory, and leave memory unused rather than use it for disk cache. From: Ushuaia Tokugawa You can easily create a ram disk on MacOS X without any third party products. that's not really a "ram disk" in the usual sense. The contents of that "ram disk" are paged in and out just like any other disk data, they're just written a bit more efficiently and they're paged to the swapfiles rather than to a directory tree on disk.