Xen

I'm currently (may/june 2006) doing some research on the usability of ASE and Replication Server with Xen virtualization (http://www.xensource.com) on Linux systems.

Quick Notes

• ASE 15.0 works OK but sofar only limited tests have been performed.
• Replication Server 15.0 is a problem. For performance reasons Xen uses its own mechanism to handle "thread-local storage" (http://en.wikipedia.org/wiki/Thread_Local_Storage) in stead of the libraries in /lib/tls. When you install a replication server and a stable device cannot be created (or only a single 16Kb allocation is made) you hit the tls bug. See below for a description to identify this issue in more detail and how to use the standard /lib/tls libraries. Further research is now focussed on the performance impact of using thread local storage from /lib/tls in combination with Xen.
• I'm using Xen version 2 but according to the Xen documentation the issue with thread-local storage is also present in version 3.

Feedback on this subject is very welcome. mailto:peter@petersap.nl

Throubleshooting Replication Server

Use the Linux ldd utility to check if the repserver binary (located in $SYBASE/$SYBASE_REP/bin) picks up the right libraries from /lib/tls. Just do a "ldd ./repserver" and check the output. You should get this: (ignore the hexadecimal numbers)

libnsl.so.1 => /lib/libnsl.so.1 (0x008b4000)
libpthread.so.0 => /lib/tls/libpthread.so.0 (0x00c95000)
libm.so.6 => /lib/tls/libm.so.6 (0x00b7f000)
libdl.so.2 => /lib/libdl.so.2 (0x00ba4000)
libc.so.6 => /lib/tls/libc.so.6 (0x00a53000)
librt.so.1 => /lib/tls/librt.so.1 (0x00736000)
/lib/ld-linux.so.2 (0x00a3a000)

Note: your output might also mention linux-gate.so.1, just ignore this.

When you get something else do one of the following, depending on your situation:

• When you have disabled tls in the process of setting up a Xen domain, reverse this step. Xen asks you to rename the tls directory in /lib to something like "tls.disabled". Rename the directory back to tls, then reboot the Xen domain.
• Check the libraries in /lib/i686. Go to /lib/i686 and rename the files libc.so.6, libm.so.6, libpthread.so.0 and librt.so.1 to something else. This might not be the best solution for everybody since these files are soft links to the actual libraries, but for repserver it works (sorry, I'm not a Linux guru). No reboot is needed since these libraries are loaded on demand.
• It still doesn't work? Send me an e-mail.

The setup if correct if you see this during booting of the domain:

***************************************************************
***************************************************************
** WARNING: Currently emulating unsupported memory accesses  **
**          in /lib/tls libraries. The emulation is very     **
**          slow. To ensure full performance you should      **
**          execute the following as root:                   **
**          mv /lib/tls /lib/tls.disabled                    **
***************************************************************
***************************************************************