Dual CPU Database Server Comparison

64 bit Software Experiences...

As we stated above, we didn't use the latest and greatest version of MySQL, but rather, we used the version that came with the SUSE SLES8 to avoid software issues. The wisdom of this decision was quickly illustrated when we tried to install DB2 8.1.2 64 bit on our 64 bit SLES 8.

To make db administration easy, IBM provides a control center, which is a very powerful tool that gives a good overview of all tables and instances. This tool runs on top of Java. We noticed that DB2cc was completely unstable with SUN's java, so we had to un-install it and install IBM's version. This might not been new to many DB2 users out there, but for us, it was a disappointment that there are incompatibilities between different JVM. After all, it was the ease of porting applications that made Java so popular.

And installing IBM java wasn't so easy. But finally after adapting profiles, paths and making several softlinks, we made it work.

The next problem was that Java 64 bit wasn't stable yet, so we had to create a 32 bit instance on top of our 64 bit database. Even then, we received cryptic messages such as "CLI0622E Error accessing JDBC administration service extensions".

At last, we came to conclusion that 64 bit DB2 8.1.2 would never run on our system. Luckily by that time, DB2 8.1.3 was out, which fixed quite a few of the problems mentioned above.

This experience shows that moving to 64 bit software is as easy as many reports might indicate. In fact, 32 bit software on a 64 bit operating system will never be 100% free of incompatibilities. System calls from a 32-bit application always need to be converted to 64-bit calls by a type of emulation layer.

As quoted by Andi Kleen:

"A system call from an 32bit application needs to be converted to 64bit. While this isn't that hard for the Unix/Linux system calls (Unix traditionally has a relatively clean and not too big interface between user and kernel space) there are lots of "backdoors" - ioctls - for various driver specific tasks. For these a 64bit kernel will likely never be 100% compatible because there are thousands of these. Of course the majority of applications don't use obscure driver ioctls, but some still do. So in short you have some risk of incompatibility when running 32bit binaries on 64bit kernels".

Don't get us wrong - it is probably 98% or so compatible. But before moving to a fully 64 bit system, you should test your 32 bit applications thoroughly on your favorite 64 bit OS.

On the bright side, we were amazed how easily Yast2 (SUSE install tool) recognized all our hardware on both Xeon and Opteron platforms. Yast2 is simply a wonderful tool that made software and hardware upgrades very easy. I used to have very different experiences with Linux and I remember vividly how I struggled to get some network cards and SCSI cards working.