Companies that use large servers will also take notice of Linux 2.6, which will support NUMA (non-uniform memory access) multiprocessor machines.
Linux’s SMP (symmetric multiprocessing) support gets a major boost with the new kernel. Although the 2.4 kernel can theoretically handle as many as 64 processors in a single system image, in practice it has only been useful in configurations as high as eight processors. With Linux 2.6, however, developers say this limit will jump to a theoretical maximum of 256 processors. In practice, 32-way SMP x86 systems will now become usable, they expect. And with 64-bit processors such as Intel’s Itanium or IBM’s Power Architecture, this practical limit will jump to 64 processors.
Though Silicon Graphics is now selling a 64-processor Linux SMP machine, the Altix 3000, it is doubtful that many vendors will jump into the 64-way Linux fray, said Dan Kusnetzky, an analyst tracking Linux for IDC.
“Right at the moment, people are not comfortable deploying tasks large enough to need that kind of configuration on Linux,” Kusnetzky said.
When Linux vendors such as Red Hat and SuSE bring out their own distributions based on the 2.6 kernel later in the year, customers will be more comfortable moving to a higher number of processors, Kusnetzky said. The analyst expects customers to remain cautious about deploying systems in the 32 to 64 processor range.
In addition to running faster on bigger servers, Linux will also run better on larger storage arrays. Developers have overcome a technical limitation that capped the number of storage devices that could be attached to a Linux system, and they have added better volume management support for storage devices. Furthermore, they have completely rewritten Linux’s I/O subsystem and added support for asynchronous I/O so that applications can run faster and more efficiently while reading hard drives.
“The people who I think are going to be storming down the door for [Linux 2.6] are people with huge amounts of disk storage,” said Chris Mason, a software developer with SuSE. The 2.4 kernels have a limit of 2TB per device, which limited the number of devices you could use with the operating system to approximately 1,000 — enough for most Linux users, but not enough for use with some Linux-based mainframes and Oracle databases accompanied by extremely large storage arrays, according to Mason. “2.6 will support up to a million devices,” he said.
These I/O performance improvements alone could make Linux 2.6 worth considering, said Jesse Crew, manager of global systems at Aventis Behring, who is running accounts receivable and electronic data interchange applications on top of the Oracle database and Linux.
“At this point, the main thing we’re looking forward to is the better volume management, as well as the asynchronous I/O, just for performance improvements,” Crew said.
Red Hat and SuSE both say that the next major release of their Linux distributions will support the new kernel, but because of Linux’s open source development process, the vendors have long had access to the most interesting new technologies in 2.6. And both, as is common practice with Linux, have already added many of 2.6’s features to their product offerings in the form of patches to the 2.4 kernel.