If you have more than one hard disk, you can improve the performance of the virtual memory further. To do so, simply install the as on one hard disk and the virtual memory on a dedicated partition on another hard disk This scheme is much better than having both on the same hard disk because it gives independent control to the virtual memory. While files are being read from or written to one hard disk, the as can operate the virtual memory simultaneously on the other it won't have to wait for either operation to complete before starting the other.

These days, it is becoming increasingly common to have more than one as installed on a computer and use (boot) anyone of them at a time. If you have more than one hard disk, you can use cross swapping to utilise all hard disks optimally. It is best to install separate ass on separate hard disks. This isolates their partition tables, provides physical encapsulation, and prevents space conflict and re-installation if you want to change partition sizes later. However, typically, only one as is used at a time. All the others remain unus~d as long as that one is being used. If the other systems are on different hard disks, those hard disks will remain unused for that time. We caQt;herefore utilise them for the virtual' memo y qf th~ 0S that is running. To do this, simp y a lot each. OS's virtucil. memory to a partition on a hard disk other than that on which the as is installed. We will look at a scenario where Microsoft

Windows'and Lnux are to be 'dual-booted. Let's suppose we have tWo hird disks:A and B We install Windows on harddisk A and a distribution 6fti£tix oh hard' " disk B. Now, to employ cross swapping. we place the virtual mern9IY for Windows on a dedicated partition on hard disk! E, wbile we place the virtual memmory for Linux on a dedicated parqtion on hm:d disk A However, to achieve, it is best to create the partitions before or while installing the operating systems. they can be created later, but that require either a RAlD/LVM set up or special software. If youwish to follow the' process,mentioned, set up your hard disk partitions as shown in Figures 1 and 2. . I
Figure 1 shows hard disk A with the first/two partitions allotted for windows file and the last partition used as decijcated virtual memory for Linux ( the swap pertotions ) Figure2 shows a similar arrangement of hard disk B with a virtual memory partition for Wmdows and the last two partitons for linnux files. The exact positioning of the partitions is such because Windows always needs the first partition of the first hard disk, and the Windows swap partition is placed at the head of the second disk because Windows sometimes achieves better performance if its v,irtual memo . partition i§ placed at the beginning of a hard disk 'The two partitions each for Windows and Linux files are just my person -preferences to ep the system and personal files separate. You can use one or more partitions in their place for each OS

To actually create such a layout during installation, start with two blank hard disks and folloW'the steps below (note: tllis assumes tve're'llsing Windows xP and so the exact steps may differ for other versions-refer to Windows documentation fDr changing the amount of virtual memory in such cases).

1. Create ,a primary partition on-the first haud disk, make it bootable (active), ,and install Windows on it (you can create the partition from withinthe windows installations program itself.

2. If you want another Windows partition for your personal files, as shown in Figure :1, create a primary partition. on the fusthard disk (Disk O) using the Windows,disk management tool (right click on My,computer, clik Mange-Disk Management.

3. Leave the area for the Lihux swap.unpartitioned at the end,of the first hard disk.(Disk O) keep about for 1.5 times the amount of your RAM reserved for this space. you can also keep 1 GB if you have 512 MB or more of RAM and want to conserve disk space.

4. If the disk management tool is not already open, right click My Computer, clickManage~Disk Management.

5. On the second hard disk (Disk 1), create a primary partition 1.5 times the size of your RAM (or 1 GB-see the above point); plus about 15 to 20 per cent of that space, assign a drive letter and format it (preferably with NTFS). Note that only Windows needs the extra 15-20 per cent of free disk space. Don't reserve any extra amount for Linux on the first disk. Close the disk management tool when done.
6. Right click My Computer, clickProperties Advanced Under Performance click Settings Advanced. Under Virtual memory click Change.

7. Select the first partition (C, click No pagingfile, then click Set.

8. Select the new partition (drive letter) you created in Step 5, then click Custom size.

9. If you allocated 1.5 times the amount of your RAM, type that amount in megabytes (l GB = 1024 MB) in both the minimum and maximum boxes, then click Set. If you allocated 1 GB, type 1024 in both boxes, then click Set. This sets up your virtual memory for Windows. Make sure not to set the whole partition space (which includes the additional 15-20 per cent space) here. The extra free space is required by Windows to perform optimally.

10. Click OK, then OK again to close the Performance Options box.

11. Click the System Restore tab, then select the partition (drive letter) you set the virtual memory in.

12. Click Settings ... then select 'Turn off System Restore on this drive' and click OK Confirm that you want to turn off System Restore on the drive.

13. Click OK to close the 'System Properties'box.

14. In your Linux installation program, select the option for custom (or expert) partitioning at the beginning of the partitioning phase (most Linux installers provide such an option, but if yours doesn't, you can use the fdisk or ifdisk program; (c )fdisk coverage is out of the scope of this article so you can get help from their manual and info pages on a working/live Linux system).

15. Select the first hard disk and create a primary partition in the space you had reserved for Linux swap at the end of the first disk. Make the partition use the full reserved (available) free space. Set it as the swap partition. This creates the virtual memory for Linux.

16. Select the second hard disk and create primary or extended partitions as you want for your Linux files after the existing Windows partition. The existing Windows partition on the second disk contains the Windows virtual memory that was set up previously.

17. Proceed with your Linux installation. Don't set the option to automatically mount the Windows virtual memory partition on the second hard disk. If your installer turns it on by itself, make sure to turn it off.