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Anyone else using Ramdisk in Windows 7?

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vlastimil:
No, quite the opposite. The swap causes the hard disk to be treated as extra memory. The Ram disk does the opposite. It blocks part of your memory and allows you to treat the memory as a disk.

That is why Stoic Joker was telling you "are using memory, to access memory, that's already in memory"  :).

justice:
But the RAMdisk just causes some hard drive space to be treated as extra memory, right-kyrathaba (August 26, 2011, 06:55 AM)
--- End quote ---
A ram disk causes some RAM space to be treated as a fast hard drive ;)

kyrathaba:
I understand now (I think).

Both page file (hard disk space treated as memory) and a RAMdisk (memory space treated as some hard drive space) can be advantageous under certain conditions, right?

kyrathaba:
Do you guys agree with the following, taken from a page on Lockergnome:

Myth - "Disabling the Paging File improves performance."

Reality - "You gain no performance improvement by turning off the Paging File. When certain applications start, they allocate a huge amount of memory (hundreds of megabytes typically set aside in virtual memory) even though they might not use it. If no paging file (pagefile.sys) is present, a memory-hogging application can quickly use a large chunk of RAM. Even worse, just a few such programs can bring a machine loaded with memory to a halt. Some applications (e.g., Adobe Photoshop) will display warnings on startup if no paging file is present."

"In modern operating systems, including Windows, application programs and many system processes always reference memory using virtual memory addresses which are automatically translated to real (RAM) addresses by the hardware. Only core parts of the operating system kernel bypass this address translation and use real memory addresses directly. All processes (e.g. application executables) running under 32 bit Windows gets virtual memory addresses (a Virtual Address Space) going from 0 to 4,294,967,295 (2*32-1 = 4 GB), no matter how much RAM is actually installed on the computer. In the default Windows OS configuration, 2 GB of this virtual address space are designated for each process' private use and the other 2 GB are shared between all processes and the operating system. RAM is a limited resource, whereas virtual memory is, for most practical purposes, unlimited. There can be a large number of processes each with its own 2 GB of private virtual address space. When the memory in use by all the existing processes exceeds the amount of RAM available, the operating system will move pages (4 KB pieces) of one or more virtual address spaces to the computer's hard disk, thus freeing that RAM frame for other uses. In Windows systems, these "paged out" pages are stored in one or more files called pagefile.sys in the root of a partition. Virtual Memory is always in use, even when the memory required by all running processes does not exceed the amount of RAM installed on the system."


Myth - "Moving the Paging File to a different partition on the same drive improves performance."

Reality - "Moving the Paging File (pagefile.sys) to a different partition on the same physical hard disk drive does not improve performance. Simply using a different partition on the same drive will result in lots more head-seeking activity, as the drive jumps between the Windows and paging file partitions. Even though moving the paging file in this case can have the positive effect of defragmenting it, the loss in I/O performance out weighs any gains. It is better to simply defragment the paging file using PageDefrag and keep maximum I/O performance by leaving the paging file where it is with a single drive setup.

Notes - However you can enhance performance by putting the paging file on a different partition and on a different physical hard disk drive. That way, Windows can handle multiple I/O requests more quickly. When the paging file is on the boot partition, Windows must perform disk reading and writing requests on both the system folder and the paging file. When the paging file is moved to a different partition and a different physical hard disk drive, there is less competition between reading and writing requests."


Myth - "Putting the Paging File on a RAMdisk improves performance."

Reality - "Putting a Paging File in a RAM drive is a ridiculous idea in theory, and almost always a performance hit when tested under real-world workloads. You can't do this unless you have plenty of RAM and if you have plenty of RAM, you aren't hitting your paging file very often in the first place! Conversely, if you don't have plenty of RAM, dedicating some of it to a RAM drive will only increase your page fault rate. Now you might say "yeah, but those additional page faults will go faster than they otherwise would because they're satisfied in RAM." True, but it is still better to not incur them in the first place. And, you will also be increasing the page faults that have to be resolved to exe's and dll's, and the paging file in RAM won't do diddly to speed those up. But thanks to the paging file in RAM, you'll have more of them. Also: the system is ALREADY caching pages in memory. Pages lost from working sets are not written out to disk immediately (or at all if they weren't modified), and even after being written out to disk, are not assigned to another process immediately. They're kept on the modified and standby page lists, respectively. The memory access behavior of most apps being what it is, you tend to access the same sets of pages over time... so if you access a page you lost from your working set recently, odds are its contents are still in memory, on one of those lists. So you don't have to go to disk for it. Committing RAM to a RAMdisk and putting a paging file on it makes fewer pages available for those lists, making that mechanism much less effective. And even for those page faults resolved to the RAMdisk paging file, you are still having to go through the disk drivers. You don't have to for page faults resolved on the standby or modified lists. Putting a paging file on a RAMdisk is a self-evidently absurd idea in theory, and actual measurement proves it to be a terrible idea in practice. Forget about it."

--- End quote ---

vlastimil:
Page file (swap) is advantageous when you run a lot of programs at once and the sum of the memory required by the programs is bigger than available physical memory minus memory used for other purposes. I'd say if sum of the memory required the programs > 50% of your physical RAM. It does not hurt much to leave it enabled (just in case) and a reasonable size is 2x your physical RAM. But with the amount of memory people have in their systems now, I see little need for it. Swap was invented in the old times, when memory was very expensive to allow programs to use more memory than there actually was.

Ram disk is beneficial if you need a small, super-fast hard disk for a special purpose. For example when compiling a very large project, where the compiler creates and accesses a lot of temporary files. In other cases, it hurts, because it blocks Windows from using the memory you dedicate to it. It is better to simply leave the applications running.

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