First, any salesman with a rule of thumb like 10:1 scares the everything out of me.... Your 1GB of storage will at most support an 800MB virtual machine. YOU CAN NOT OVERCOMMIT STORAGE if you only run one virtual machine. You can ONLY make the virtual machine small enough so that it fits in the VM pageable storage that is available. YOU CAN overcommit if you have several servers, and many of them are idle as long as no Linux server is larger than what you have.
Other platforms fix any performance problem by adding memory. On the "z" platform, we have many other options, thus the memory requirement will be greatly reduced by going to "z". In your case, it is not only memory or storage i'd worry about, but there are tuning options. There are few easy tuning options at the point where your processor or channel is saturated. And LVM uses more CPU, in my one measurement using FTP, LVM caused throughput to decrease because the processor was saturated and LVM uses more CPU.... Carsten is right about the ficon. But i've had issues with the price of the ficon channel. If you are trying to do this with what you have, that cost may be prohibitive. As for the rest of Carsten's comments, i'm mostly in agreement (which probably surprises him, we usually only agree on beer) but the big problem i see is that there is no measurements published anywhere comparing platforms. Just a lot of opinions. I've been involved in some benchmarks recently looking at database and other file activities and don't think that the I/O on the other platforms really consumes much of the processing - leaving not quite the advantage that you might have heard.... There is a LOT of interest in this kind of apples to apples comparison, but other than the little that I've published, I've not seen anything else. But watch this space. There is an Oracle redbook (in which I am participating). Hopefully some good data will come from that. And there is an effort to begin some scalability testing as a joint project between Oracle, IBM and Velocity Software. >Date: Thu, 19 Aug 2004 09:47:49 -0400 >From: Carsten Otte <[EMAIL PROTECTED]> >To: [EMAIL PROTECTED] >Precedence: list > >Hi Doug, > >you should consider using ficon attached storage on the z800 for >database workload. In addition, consider using LVM striping over >multiple volumes or alternatively LVM multipath on parallel >access volumes to get your IO thoughput up to a reasonable >level. With regard to memory size, you do have some advantages >when running on a Mainframe with z/VM. One is, that z/VM will be >able to swap out servers that are currently idle and/or not >driving loads of IO at the moment. The other one is, that your >memory bandwidth and the cache sizes are much faster then on >other platforms. The amount of memory overcommitment strongly >depends on your workload, a factor of 10 can indeed be valid in >rare scenarios. However, most scenarios do lead to very crappy >performance when using a factor 10 overcommitment ratio. With >regard to PU horsepower, you do indeed have less horsepower on a >z800 IFL than on your previous system, but unlike on Intel IO >does not eat up your PU because IO processors handle it and >because of decent memory bandwidth your PU will spend less time >on waiting for your memory to deliver data. Since database >workload is not too computing intensive but does cause a lot of >IO, CPU utilization may not become a problem afaics. > >with kind regards >Carsten Otte "If you can't measure it, I'm Just NOT interested!"(tm) /************************************************************/ Barton Robinson - CBW Internet: [EMAIL PROTECTED] Velocity Software, Inc Mailing Address: 196-D Castro Street P.O. Box 390640 Mountain View, CA 94041 Mountain View, CA 94039-0640 VM Performance Hotline: 650-964-8867 Fax: 650-964-9012 Web Page: WWW.VELOCITY-SOFTWARE.COM /************************************************************/ ---------------------------------------------------------------------- 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
