Paging Space Placement Best Practices

Answer

1- Assign only one paging space per physical disk.
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Paging space is allocated in round-robin manner, and use all paging areas equally.
Spreading paging activities over multiple physical volumes boosts paging space performance.

2- Do not extend a Paging Space over multiple physical volumes.
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Do not extend one paging space over multiple physical volumes.
Because, round-robin technique treats paging area as single paging area.
Therefore, the activity is not evenly spread across the disks.

3- Create all paging spaces with the same size including hd6.
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Paging spaces should be the same size, if paging spaces are not the same size, the smaller paging areas will fill faster because of the round-robin technique.
Hence, paging space usage is not balanced.

4- Assign paging space to the least active disks.
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Paging space performs better when it’s not competing with other activities on disk.

5- Use SAN disks for better performance.
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Using SAN disks generally results in better throughput when reading/writing to the disk.
Also, SAN controllers have large cache which will store the frames which paged-out to disk.
If the page frames are required to be back-in and the data still in the cache, the system will not have to read from disk, which reflects on performance positively.
However, we still need to balance this by taking into consideration the possibility that we may lose connection to the SAN storage.

6- Mirror all page spaces that are on internal or non-raided disks.
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AIX crashes if it lost the in-use paging volumes, and will not boot without hd6.
Mirroring paging volumes will decrease the possibility of losing paging space.
Also, Don't ever place a paging space on a removable disk drive.
AIX will crash if the disk is removed.

7- The total amount of paging space directly depends on the application and the system usage, and it is often determined by trial and error.
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Paging Space size is unique for each system, depending on such things as which applications are running and/or the number of active users.
One commonly used method for memories larger than 256 MB, total paging space = 512 MB + (memory size - 256 MB) * 1.25
This formula is just an initial suggestion for the paging space size, you maybe require to adjust the size at anytime that best fits your environment.
For an example, for systems with large amounts of memory > 64GB typically do not need such large amounts of paging space.

8- Single paging space device size can't exceed 64GB.
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Each single paging space area (hd6, paging00, paging01...etc) can't exceed 64GB.
However, total of all paging areas can exceed more than 64GB without a problem.