<[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED] -cell00.bisx.prod.on.blackberry>... > I am surprised! > I asked a question regarding the performance of the two types of drives within a single frame, running with z/OS. > > I stated that we had been told that 146 was not good about six months ago, by our out-sourcer. > Now, we are hearing differing stories. > > I asked for anybody who knew anything about it. > And, I have seen ZERO responses on IBM-Main. > > (I received one offline response, and it only talked about 73GB drives). > > Surely, on such an opinionated forum as this, somebody must have something to say! >
Ok, I'll bite. A couple of things went through my mind when I read your question, but none were really answers, so didn't post them then, but here they go: 1: the main part of your performance should be delivered by the cache; your hot applications should not need a lot of backend I/O. Search the archives for my lengthy thread in the beginning of this year on DB2 Log Archiving problems after moving to an ESS. The point was that DB2 was logging at cache speed (100% cache hits on writes), but Log Archiving had to read from the backend, because the data was already destaged and discarded from the cache, partly due to the amount of cache, partly due to the caching algorithm that supposed that sequentially written data can be preferred for destaging. This caused problems at moments of heavy logging when the logs were filled quicker than they were emptied and finally they were all full, causing DB2 to halt. 2: the 144GB disk rotate at the same speed as the 72GB, so basically they can deliver the same amount of MB/sec. The problems can arise from contention on 2 places: 2a: at the disk level, since the 144GB contains more data, potentially more I/O can cause more disk contention. 2b: at the rank level. In the above mentioned thread experts explained that a rank can deliver 40 MB/sec. So by putting more MBs on a rank with 144GB you can reach this bottleneck earlier. So, in summary, the disks, 72 or 144, should not be involved in your main performance and when they are, the 144GB disk don't cause a problem by themselves, but they can throttle your disk system more rapidly than 72GB disks. Hope this triggers others too, Kees. ********************************************************************** For information, services and offers, please visit our web site: http://www.klm.com. This e-mail and any attachment may contain confidential and privileged material intended for the addressee only. If you are not the addressee, you are notified that no part of the e-mail or any attachment may be disclosed, copied or distributed, and that any other action related to this e-mail or attachment is strictly prohibited, and may be unlawful. If you have received this e-mail by error, please notify the sender immediately by return e-mail, and delete this message. Koninklijke Luchtvaart Maatschappij NV (KLM), its subsidiaries and/or its employees shall not be liable for the incorrect or incomplete transmission of this e-mail or any attachments, nor responsible for any delay in receipt. ********************************************************************** ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
