How MPE Balances New Disk Space
February 28, 2014
If we have a system (volume set) with mostly full disks, and I add a new big empty disk to it, how will MPE/iX do all new allocation on that disk — will it wait until it fills up to the same relative fullness as the existing drives?
See, we have a system with a Nike Model 20 and a bunch of RAID 1 LUNS, and we’ve added five new drives in RAID 5 to the system volume set. But that sounds like we’re on the cusp of a disaster, because while the read performance is measurably better, all the system is going to be doing is writes to this drive for every new extract and scratch file. And as everybody knows, the write performance is like 2.8 times slower to the RAID 5 LUN than the RAID 1 LUN.
[Corrected, to identify the BALANCE command as a part of DeFrag/X.]
Craig Lalley noted, "There is a command you will want to use if you have Defrag/X, [created by Lund, sold by Allegro] The command is BALANCE VS. As an example,
"There’s online help for this command in Defrag at HELP BALANCE. Without that, I would use system logging to determine the most heavily accessed files and store/restore them to spread the extents."
And there's also help to manage this kind of balancing and defragmentation from VEsoft, as well as that Lund tool.
Continue reading "How MPE Balances New Disk Space" »