As Bill Bitner would say, "It Depends. With Linux it depends even more..."
It depends on the nature of your hardware and the nature of your computing load. A small CPU with a small amount of memory and slow disk drives will have trouble. The oft-quoted experiment with "thousands of servers" ran some 40,000 identical Linux images with apache webservers all serving the exact same page with almost none of them actually being accessed. One the other hand, I am informed that Deutche Telekom and Bank of Venezuela do run over a thousand active linux servers on the mainframe with no problems. We ran 42 Linux servers, mostly Apache and Samba, on a 2-IFL z800 system with 8GB of memory and very old (7 years old), slow DASD with no problems other than the occasional performance problem with Java or Tomcat. We had capacity to spare and figured we could handle 300-500 servers. Then we added 8 Oracle 10G servers at around 1GB virtual each and things started to slow down considerably, even moving to 11GB of memory. We're running about 50GB of virtual working sets in 8Gb of main memory and 3GB of expanded. Basically, Java, Tomcat, JBoss, Websphere and the like use lots of CPU cycles. they can max out your CPU in no time. Oracle and multiple Java processes (e.g. Websphere) and the like use lots of memory. VM paging and linux swapping to slow DASD just makes it worse. You can (and we do) move Linux swapping to V-disk and take advantage of expanded storage, which essentially moves Linux swapping to VM paging, but if your DASD is slow, you will see slowdowns and page waits. Some people are like Slinkies... Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs. Gordon Wolfe, Ph. D. (425)865-5940 VM Technical Services, The Boeing Company > ---------- > From: Glenn Nicholas > Reply To: Linux on 390 Port > Sent: Wednesday, July 20, 2005 9:09 AM > To: [email protected] > Subject: Hundreds or Thousands? > > A question about Linux on z/VM and scalability. > > Early tests of Linux on 390 (Test Plan Charlie and Omega) > demonstrated that thousands/tens of thousands of virtual Linux > servers could physically be supported by z/VM (and I note with > respect that Sine Nomine has a presence in this forum). These days > IBM steps up to the plate in public for 'hundreds' of virtual servers > (ibm.com), and Charlie/Omega aren't referred to as frequently. > > There is a big gap between hundreds and thousands. My question ... > is zVM (with up to 16 engines) really capable of supporting thousands/ > tens of thousands of servers in the real world, and IBM just being > coy? Or is it really hundreds? If it is in the thousands, is this > theoretical, or are there really customers using it at this level? > For the purposes of this question, let us assume a 'server' is used > by a small business of 10-20 employees with several hundreds of > customers, supporting web site services and email (in a penguin > colony with non-uniform resource demands). Vague, but hopefully a > pointer to something useful. > > I recognise that this question is dependent on a wide range of > variables. These would include the fact that the actual workloads > encountered will matter a great deal. > > Possibly there are many opinions about this, and no one correct > answer, but I am very interested in hearing perspectives from those > with first hand experience. Apologies in advance for asking such an > open ended question, or if this question has been tackled in depth > previously. I could find no references in the FAQ or recent postings. > > If there is a more useful way of defining a standard small business > workload that you are aware of, please comment using that as a base. > Before you criticise my lack of precision on workload, I hope you can> > comment on the basic question (admittedly posed from a perspective > that is less technically informed on z/VM than most participants in > this forum). > > Personal disclosure: I am a former IBMer, from the business > consulting group rather than hardware/zSeries. My interest is in the > potential commercial application of Linux on zSeries, beyond server > consolidation. If this isn't the correct forum for this question, > please forgive in advance, and point me to a better forum. > > Glenn Nicholas > Holipac. > > ---------------------------------------------------------------------- > For LINUX-390 subscribe / signoff / archive access instructions, > send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit > http://www.marist.edu/htbin/wlvindex?LINUX-390 > > ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
