We are running with the 4.18 kernel so the issue itself is solved. If anything, we might go to version 5.0, I don't think we want to go back to 4.15.
But as for large disk sets, if it wasn't for our indexing service we could run our Samba machine in 400MB. That includes an LVM with 40 disks (model 9). Apart from a few K for each disk I wouldn't expect the size of the machine to be so dependent of the number of disks. I would expect the memory size of a system depends on the application instead of the amount of (potential) storage in a filesystem. We have a TSM server that has 72 disks (model 54). We have 2G assigned to the machine, but I think it could even run happily in 1G (or maybe even less). Met vriendelijke groet/With kind regards/Mit freundlichen Grüßen, Berry van Sleeuwen Flight Forum 3000 5657 EW Eindhoven -----Original Message----- From: Linux on 390 Port <[email protected]> On Behalf Of Frank Heimes Sent: Tuesday, November 12, 2019 2:45 PM To: [email protected] Subject: Re: Ubuntu 18-04 unable to add DASD Hi Berry, thanks for the add. background info. I just wondered, because small system are okay (and still often used on s390x) - and our minimum is - as of today- 512MB (even if we recommend 1GB +). When I came across installations with several 'smaller' systems, they had usually very few resources overall (incl. disks - mostly just one or a handful, due to partial filesystem sharing). In your case a smaller system is used in combination with a larger set of disks - hence my question. But looks like you're preparing biggers systems with the help of a smaller one - I see. I'm glad that you can keep going with your (bigger) 32GB system - or alternatively with using the HWE kernel. I'll keep you posted on the kernel 4.15 update ... Bye, Frank On Tue, Nov 12, 2019 at 2:17 PM van Sleeuwen, Berry < [email protected]> wrote: > Hi Frank, > > I started with an installation in 900M. For the installation itself > it's good enough but when additional disks were activated I ran into problems. > Later I tried in 2G with the same problem. Only when I moved to the > target guest (32G) I could successfully enable the application disks. > And then I could really see the cause of the problem. When I activated > disks the memory usage reported in top was 2.6GB. And I guess, since > it's hardware related memory, it is not eligible for swap so the > system tries to swap other processes and eventually the oom kills even the > critical processes. > > Indeed 20 disks might just kept you out of problems but probably you > were already close to the edge. > > Depending on the purpose of the server, we have a lot of small servers. > (In the past even as low as 130MB.) We have found that for a Suse > zypper update we minimally require about 400MB so that's our baseline > for some servers. But even an active Samba machine only has 900M, > mostly because of an indexer process that requires quite some memory. > Our case for Ubuntu is Machine Learning and this server is currently > defined with 32GB, so I could quite easy go into that server to see > what was going on after the base installation. > > Met vriendelijke groet/With kind regards/Mit freundlichen Grüßen, > Berry van Sleeuwen Flight Forum 3000 5657 EW Eindhoven > > -----Original Message----- > From: Linux on 390 Port <[email protected]> On Behalf Of Frank > Heimes > Sent: Tuesday, November 12, 2019 12:22 PM > To: [email protected] > Subject: Re: Ubuntu 18-04 unable to add DASD > > Hi, > I just completed some rough tests on a pretty small LPAR (just 1.,5GB > RAM) and I ran the GA kernel 4.15 as well as the HWE kernel 5.0. > > An activation of another DASD device requires on kernel 5.0 about 90% > less memory compared to kernel 4.15 - so there is indeed a big difference. > However, with the 20 DASDs that I had left for the test I wasn't able > to run in an OOM situation, but the memory left decreased consistently... > > Berry, may I ask how big the system is that you are using (regading RAM)? > > Bye, Frank > > > This e-mail and the documents attached are confidential and intended > solely for the addressee; it may also be privileged. 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