Quote:
Originally Posted by
Scrutinizer
Hi, paging space should most certainly be mirrored.
You are right. The paging space contains program code that does not fit into RAM. Imagine what would happen if the single disk that contains the paging space fails. The effect would be as if you lose a memory chip. Therefore you definitely mirror your paging space if you mirror your rootvg already.
Quote:
Originally Posted by
Scrutinizer
IMO mirroring paging space will not impact performance very much and may even improve performance in some cases.
I do not know what your AIX background is but as you answer questions about AIX memory management you must be experienced. However, I think here you took the wrong turn.
If you use dedicated SCSI disks for you rootvg those disks usually deliver about 150 to 300 IOPS. With those the disks turn to 100% busy and from then on your GHz Power CPUs (with currently around 4.000.000.000 cycles per second) sit there idle. Improve performance? Well... probably in a micropartion environment you manage to completely deactivate the CPU cycles for the server paging and transfering the cycles to other LPAR - these might then indeed improve their performance.
If you use SAN disks for the rootvg you may get a higher number of IOPS but never get close to anything taking place in RAM. More likely using the SAN that way will interfere with other servers that use the same physical disks in the underlying SAN boxes. So again the impact on performance is huge.
Therefore you do not want the paging space being used. Mind that I do not say that there must be no paging space. But paging space is meant as a last resort in case an unexpected request for more memory appears. An AIX administrator will always strieve for calculating how much memory the server's applications need so that it runs in RAM and make that amount of RAM available. An AIX server that uses paging space all the time is not sized correctly.