RE: IO Freeze ON RHEL 6.6 and hence high log file sync

From: Mark W. Farnham <>
Date: Wed, 18 Apr 2018 18:11:29 -0400
Message-ID: <009901d3d762$341f7500$9c5e5f00$>

LOL., JL. Probably an elevator algorithm on failures. It was probably telling someone they'd better copy the contents somewhere real soon now and retire the device.

Last time I saw wasn't RHEL but actual UNIX and the root cause was no flap on the read_only button that was far too easy to bump.

I don't even know if newer disk farms have a read_only button.

-----Original Message-----

From: [] On Behalf Of Jonathan Lewis
Sent: Wednesday, April 18, 2018 3:51 PM
Subject: Re: IO Freeze ON RHEL 6.6 and hence high log file sync

The last time this happened to me it was because the disk system had decided to do a diagnostic self-check every 15 minutes - I can't remember why, though.

Jonathan Lewis

From: <> on behalf of Purav Chovatia <> Sent: 18 April 2018 18:25
Subject: IO Freeze ON RHEL 6.6 and hence high log file sync

We are on RHEL 6.6 running a 2-node Oracle 12c RAC.

All of a sudden, for 2-3 minutes, DATADG (asm diskgroup containing all data files) freezes for 2-3minutes with iostat showing 100% utilisation, very high svctm and very high write_await. But the r/s, w/s rsec/s and wsec/s is 0. Meaning no IO but still disk fully busy. So it's like a freeze.

Has anybody experienced this and can somebody help as to what could be the reason?

Transparent huge pages were not disabled and general huge pages were not configured. Now both done.

Many thanks

-- Received on Thu Apr 19 2018 - 00:11:29 CEST

Original text of this message