> On Thu, 20 Jul 2023 at 09:01, Rob van der Heij <rvdh...@gmail.com> wrote: > It would be interesting to see your evidence of IBM Z not performing well > with Linux.
Linux on z performs better than Linux on most other hardware. My point is that Linux wastes much of z hardware. Since I haven't seen Linux on z, I have to make some assumptions. It's probably fair to say the Linux filesystem still uses block allocation. Let's say it's a 10 disk filesystem and 100 people are writing 1 block repeatedly at the same time. After each writes 10 blocks, where are the 10 blocks for a specific user. In z/OS you know exactly where those blocks would be in the file. If you read that file are these blocks located sequentially. While the filesystem can make a few decisions, it's nothing close to the planning provided by SMS, HSM, SRM and other z/OS tools. Like MS Windows disks, Linux filesystems can benefit from defrag. Also consider when Linux needs more CPUs than available. Clustering must be implemented on Linux to increase the number of CPU which does not share the filesystem. In z/OS, a second box has full access to all files because of Sysplex. I'm sure IBM has made improvements but some design limitations will be difficult to resolve without the correct tools. For instance, can DB2 for Linux on z share a database across multiple z frames. It's been a while since I last looked but DB2 for z/OS was used because it outperformed DB2 for Linux on z.
