> -----Original Message----- > From: IBM Mainframe Assembler List <[email protected]> > On Behalf Of Jon Perryman > Sent: Monday, August 7, 2023 11:05 PM > To: [email protected] > Subject: Re: Will z/OS be obsolete in 5 years? > > > On Thu, 20 Jul 2023 at 09:01, Rob van der Heij <[email protected]> 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.
Yes but do you really? If you allocate a fixed file size you are wasting the un-used space at the end of the file, or if you run out of space its going elsewhere. I would argue that Linux is better at using disk capacity as you only ever waste half a block. Yes they might be scattered but how much data is on spinning disk and how much on SSD? > 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. > If the data is in a SAN multiple systems can access them without a 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. Why use DB2? Dave
