Edit: The link to AIX Down Under no longer works. The link to the whitepaper no longer works.
Originally posted May 25, 2010 on AIXchange
A customer recently asked me about the default user ID length in AIX and how to change it. A quick search brought up the two-part answer.
1. To get the current value, run getconf LOGIN_NAME_MAX or lsattr -El sys0 -a max_logname.
2. To set the size limitation to a new (higher) value, run chdev -1 sys0 -a max_logname=# (where # is the new maximum user name length).
Then just a few days later, I noticed a new AIX blog, Anthony English’s AIX Down Under, covering this very topic. Anthony expounds on this subject by explaining the benefits of longer usernames. Check it out.
As for me and this blog, as promised, I can now tell you a bit about working with the new Model 780.
I was looking forward to using the 780 because I wanted to try out TurboCore mode. For a primer to this to this new feature, I suggest the IBM whitepaper, “Performance Implications of POWER7 Model 780’s TurboCore Mode.”From IBM: “The POWER7 Model 780 system offers an optional mode called TurboCore which allows the processor cores to execute at a higher frequency — about 7.25 percent higher — and to have more processor cache per core. Higher frequency and more cache often provide better performance. TurboCore is a special processing mode of these systems wherein only four cores per chip are activated. With only four active cores, ease of cooling allows the active cores to provide a frequency faster (~7.25 percent ) than the nominal rate. Both the higher frequency and the greater amount of cache per core are techniques for providing better performance. It is not uncommon for a longer running, even multi-threaded workload accessing largely private data to see a performance benefit well in excess of what might be expected from the better frequency alone. Even more complex workloads residing in a partition scoped to the cores and memory of a given processor chip can see similar benefits.”
I’d read that you needed to go into ASMI to make the change to TurboCore mode on the 780, and it was an extremely simple option to change. So I logged into ASMI, clicked on Performance Setup, TurboCore setting, changed it to enabled, and saved the settings. It was almost anticlimactic for me, and the customer is happy with the performance.
In fact, I’ve now installed each of the new models — the 750, 770 and 780 — and my customers are all pleased with the performance of the machines. How about you? Post your impressions of the POWER7 gear in Comments.