Slow I/O under load with RHEL 5.7 compared to RHEL 4 and RHEL 6
Issue
- A significant slowdown in I/O in RHEL5 (all releases, including RHEL5.9) when the machine is under load.
- The exact same workload on RHEL4 or RHEL6 does not show this problem.
- The slowdown occurs both writing to NFS or to a local disk.
- Happens on a freshly rebooted machine as well (so not because of the pagecache contents)
- Are there any kernel tunables?
Environment
- Red Hat Enterprise Linux 5 -all release streams up to and including RHEL5.9.z (2.6.18-348.15.1.el5 released July 22 2013) and RHEL5.10GA-beta. Later versions or RHEL5 may be affected too, at the time of writing no fix has been committed.
- RHEL4 and RHEL6 and later are specifically NOT affected.
- we're waiting on details of the customer benchmark/workload.
Subscriber exclusive content
A Red Hat subscription provides unlimited access to our knowledgebase, tools, and much more.
