Linux and KVM Activities Providing Foundational Support for Use of OSS

2.1 Investigation and testing of new RHEL releases

For each major release^*1 of RHEL, Red Hat offers minor releases^*1 to fix bugs and security vulnerabilities approximately every six months. Red Hat conducts testing before releasing them so they can be used safely for enterprise services.

However, system administrators tend to be conservative when considering whether applying software updates is necessary because doing so can affect the end users of their enterprise services and incur a substantial cost. This is why an even stronger guarantee of stability is required in our group.

For this reason, with the release of each minor version, certain items need to be checked on the kernel and virtualization software to prevent problems from occurring. Specifically, we check:

On the basis of the results of these checks, we decide whether the new version can be used safely in our group, and if so, we recommend it as a recommended version. As an example, for RHEL 6.4 in February 2013, we temporarily deferred making it a recommended version since it failed to pass item (3). The following is a detailed description of how we reached that decision.

2.2 Performance testing

For the newly released RHEL 6.4, as we always do for each minor release, we did some performance tests on a bare-metal server and virtual machines, using KVM for example, to determine whether there were any significant performance changes in the basic functions of the OS. The details of the measurements taken for these tests are given in Table 1.

Table 1. Benchmark tools used in our performance testing.

2.3 Disk I/O problem with RHEL 6.4 KVM

On a KVM virtual machine, the disk I/O (input/output) performance test result showed that throughputs for a particular I/O pattern dropped 20% compared to the RHEL 6.3 environment. Since this was a significant change in performance, we temporarily deferred making RHEL 6.4 a recommended version in cases where it would be used for KVM virtualization, and we further investigated the issue.

As a result of the investigation, we reached the conclusion that what had triggered the performance regression was a bug in QEMU—the machine emulator and virtualizer—that could disable a disk I/O optimization.

We also confirmed that by using a later version of QEMU that had received a bug fix patch, we could gain the same performance as RHEL 6.3 (Fig. 2). Finally, on the basis of this result, we decided to recommend the use of the QEMU version that included the bug fix for RHEL 6.4 KVM virtualization [1].

Fig. 2. Disk I/O performance test results (KVM environments).

This is an example of how our testing can prevent problems from occurring in real systems. We plan to continue this kind of testing so that our group companies can use RHEL with confidence for enterprise services.

2.4 The next major release (RHEL7)

Red Hat is now preparing to release RHEL 7, the next major version. RHEL 7 is expected to have improved scalability and many new features, so it will most likely become one of the most widely used operating systems in the future.

Accordingly, in preparation for its release, we are strengthening our know-how of RHEL 7, checking its stability, and feeding back any problems found to Red Hat and the OSS community to ensure that it is reliable.

4.1 Issues in promoting KVM

Although we have been working on KVM, it is not widely used within our group. One of the reasons for this is that the operations management features for KVM virtual environments are still inadequate.

Current popular proprietary (non open-source) products that have operations management features generally provide a GUI (graphical user interface) enabling various tasks to be performed easily even if they are complex. On the contrary, there was no such product for KVM, and depending on the task, many commands had to be entered through a CUI (command-line user interface). In this way, the lack of operations management features had been an obstacle to promoting KVM.

4.2 OSS virtualization management products: RHEV and oVirt

The oVirt community was created to develop an open source management product for KVM. Red Hat is testing and improving the product developed by the oVirt community to achieve the quality necessary for enterprise use and is releasing it as RHEV (Fig. 3). Many of the operations management features needed for KVM virtual environments are already implemented in RHEV, and efforts are continuing to add new functions and to improve its quality. We have confirmed that RHEV has no major bugs in its frequently used features and is ready for practical use.

Fig. 3. Centralized management using a virtualization management product.

To promote KVM, we will continue working on RHEV and on improving the quality of RHEV and oVirt by feeding back the know-how we gain to the oVirt community.