RAM Disks

[Fearless Leader]

Ok I was doing some random research today and found out you can just make ram disks out the ram you have installed on your computer, using some command line entries or a nice free app Ram Disk Creator.

Anyways I wanted to test the speed of my new 512mb drive and all I can say is holy crap.
The one on the left was the ram drive...

 

[CanadaRAM]

Well, yes. RAM is about 20 times faster than a hard drive.
But it's a #^#*$ if you crash or turn the machine off without backing the RAM disk up to the hard drive. And the size is limited, obviously, by the amountof physical RAM in your machine that can be allocated to RAM disk.

This is why all of the interest in large cache RAM on hard drives, and in Flash based drive caches, trying to minimize the number of times you have to go to the drive for data.

But in reverse, it is a good example of how much slower a hard drive is, when you don't have enough RAM and the OS is forced to page out to the hard drive.
You can see where the speed penalty is coming from.

 

[MisterMe]

Ok I was doing some random research today and found out you can just make ram disks out the ram you have installed on your computer, ...

RAM disks are an anachronism from a bygone era. There was a time when it was possible to install more RAM than your OS and applications could use. In the current era of pre-emptive multitasking multiuser virtual memory operating systems, RAM disk "robs Peter to pay Paul." Your Mac's virtual memory system uses all available RAM. Any extra RAM needs are mapped to your hard drive. RAM disks reduce available RAM. This causes your OS to access virtual memory earlier than it would without the RAM disk. If you are doing real work, then a RAM disk will have minimal positive impact on your productivity. OTOH, if running benchmarks is your speed, then a RAM disk may just be the ticket.

 

[Fearless Leader]

RAM disks are an anachronism from a bygone era. There was a time when it was possible to install more RAM than your OS and applications could use. In the current era of pre-emptive multitasking multiuser virtual memory operating systems, RAM disk "robs Peter to pay Paul." Your Mac's virtual memory system uses all available RAM. Any extra RAM needs are mapped to your hard drive. RAM disks reduce available RAM. This causes your OS to access virtual memory earlier than it would without the RAM disk. If you are doing real work, then a RAM disk will have minimal positive impact on your productivity. OTOH, if running benchmarks is your speed, then a RAM disk may just be the ticket.

true but say you have multi gigs in your mac say 10 in a mac pro, its great.

 

[MisterMe]

true but say you have multi gigs in your mac say 10 in a mac pro, its great.

Are you sure? My personal experience with RAM disks leads me to believe that the "placebo effect" plays a large role in the perceived speed gain. We hear all the time that RAM is much faster than hard drives. However, things are not as simple as that. RAM is accessed in 32-bit or 64-bit words. RAM disk simulates a real disk which reads and writes bits serially. It is faster than a real disk, but not enough to be more than a gimmick for most users.

 

[Fearless Leader]

^^
Im not following you but ram disk are definitively faster, around 100 to 200 times.

Anyways it'll work wonders for a hd capture im doing and felt like sharing this bit of info with the world, though as stated before it can become counterhelpful if you don't have many gigs of ram for osx and its apps to frolic upon.