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Here's the setup: my OS is installed on a 60G SSD. It is replacing a 40G SSD -- 40G just wasn't enough space for the OS partition because of the 8G of RAM in this system. Question is, would keeping the 40G SSD and putting the swap file on it improve speed? I'm thinking it might because that would be two SATA channels instead of one. E.g. when accessing a program on the 60G SSD any swap file access would go thru a separate SATA channel. But I don't know enough about SATA to say that this would be a speed improvement.

Update: Tested this with SiSoftware Sandra Physical Disks test.

Before (40G SSD only): 200.60MB/s
60G Vertex2 only: 202.09MB/s
60G Vertex2 + swap on 40G Vertex: 226.83MB/s

So a 10% performance improvement from placing the swap file on the secondary SSD. All told, not that impressive. It might be worth putting the "Users" folder on the small SSD and the Windows partition on the larger SSD.

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I'm interested in why the amount of RAM has any influence on the SSD space required. Hibernation? Giant page file/swap partition? Why not make it smaller–you don't need 12GB of virtual memory. –  oKtosiTe Dec 11 '10 at 19:13
    
Windows 7 by default wants to set the swap file size to the same as the memory. I've heard that the default settings for swap files are best. –  jcollum Dec 11 '10 at 20:41
    
Great update and information, kudos for benchmarking! :) –  HaydnWVN Apr 12 '12 at 9:41

3 Answers 3

up vote 2 down vote accepted

If both disks are installed, then an increase in performance requires that the controller is capable of handling multiple drives simultaneously in parallel. This must be verified, which kind of SATA-IO Port Multiplier you have.

As swap is rarely used, this is also a real waste of an SSD.

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rarely used? MS says otherwise: "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." –  jcollum Dec 11 '10 at 19:06
    
Who said anything about Microsoft? I thought they called it a page file... –  oKtosiTe Dec 11 '10 at 19:10
    
Used in this case means allocated, not written (unless RAM is exhausted). And if this is Microsoft, then swap/pagefile can only be put on the boot drive. –  harrymc Dec 11 '10 at 19:12
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you're incorrect. I've put my pagefile on the D drive. It's easy to do. In fact, I can have multiple swap files. –  jcollum Dec 30 '10 at 16:53

Unless you handle a REALLY big amount of data, id say your swap would never be touched, in fact, it would cause overhead so i doubt of its usefulness altogether. If you still want to keep your swapfile on another disk i say it would of cause even more overhead as one SATA controller would of have to manage two disks...

I dont have any proof nor documents to back this, its just what i think would happen :)

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I've read articles that state that removing the swap file completely actually reduces performance. That would seem to run against what you are saying. –  jcollum Dec 11 '10 at 17:09
    
I just say that having 8GB of RAM will make your computer laugh at anything you can throw at it nowadays. –  Machinarius Dec 11 '10 at 17:31
    
I would say it really has to do with your OS and what programs your running. I assume your using some *nix? I have an ubuntu machine that i do processing on and I have 8gb ram. I still use about 1-1.5gb swap under normal operation –  madmaze Dec 11 '10 at 17:34
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@madmaze: Win 7 64b (which I'm using) supports 16GB. –  jcollum Dec 11 '10 at 19:08
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@OKtosite: see that's the thing: it's hard to find any real information about this; some people say x amount of swap, some people say no swap etc. I'm gonna benchmark both. –  jcollum Dec 11 '10 at 19:46

If you can, and are desperate to boost speed of your swap (page file, whatever you want to call it), it may be possible to put it on both disks using RAID0 or equivalent. This seems like gilding the lilly unless you find yourself paging out a great deal.

Possible methods:

  • Software RAID: Create a partition on each disk, use software RAID to put them together in a RAID0 array.
  • Swap file on both (Linux will let you give the two equal priorities, I don't know about Windows)
  • Hardware RAID (will cost you an additional SSD, probably not worthwhile.
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Windows can deal with multiple page files just fine. In fact, if it need to write to a page file and multiple page files are available, the kernel will write to the page fire on the least busy drive. Putting a page file on a RAID-0 would be defeating the kernel's load balancing mechanisms. –  afrazier Dec 15 '10 at 5:29

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