Details
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Improvement
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Resolution: Fixed
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Minor
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Lustre 2.2.0
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None
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1
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4615
Description
Deprecate the RHEL5 2.6.18 kernel support for Lustre servers in the 2.2 Lustre release. Maintaining the server and ldiskfs patches and compatibility in the Lustre code is a non-trivial amount of work. RHEL5 itself is nearing the end of its support window (it is approaching 5 years old, the 2.6-rhel5.series file was added to Lustre in August 2007). The customers that are still running RHEL5 instead of upgrading to RHEL6 are very unlikely to be upgrading from Lustre 1.8 to Lustre 2.2 for exactly the same reasons (stability, lack of system testing resources, uptime requirements, etc).
In addition to this ongoing maintenance effort, there is functionality missing from the RHEL5 kernel VM/VFS that is making ongoing work like the CLIO RPC restructuring (ORI-255, others) difficult or impossible to implement correctly. The client VFS dcache interface has changed significantly in Linux 2.6.38 and later, and the need for ongoing compatibility is making the llite code increasingly complex. Similarly, the ZFS code does not work on the RHEL5 kernel for the same "lack of API" reasons.
Maintaining compatibility for the 2.6.18 kernel that is over 6 years old (released Sep 2006) keeps a lot of cruft and complexity in the client and server code (see lustre/autoconf/lustre-core.m4 for all of the kernel API changes we need to handle). The kernel developers make no effort to keep the APIs stable, and the more kernel versions we have to support the more complex our code has to become to compensate.
This bug depends on TT-268 and TT-246 in order to disable RHEL5 server build and autotest before it can be landed. We may want to do this on the orion branch first (TT-242) in order to avoid causing problems with master.
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