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

From: Ls Cheng <>
Date: Thu, 19 Apr 2018 00:22:59 +0200
Message-ID: <>

I have seen this behaviour for several reasons but all HW related, HBA saturation, faulty fibre cable, Storage Saturation.

I went through one of this last saturday, I had to call the storage admin because I was migrating a couple of database from Solaris to Exadata, the answer as always was that the array was all green light and only 30% CPU busy but he cut the storage replication just in case, after he cut the replication my migrations started to fly.

On Wed, Apr 18, 2018 at 7:25 PM, Purav Chovatia <> wrote:

> 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 - 00:22:59 CEST

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