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

From: Purav Chovatia <>
Date: Fri, 20 Apr 2018 22:57:43 +0530
Message-ID: <>

The storage is a direct-attached one. I suspected hardware to be the cause for a long time but now I think there might be a different reason. That is because it happened in January and then directly in April. Then we switched to DR site and it happened the very next day and since then it has been running fine. So it would be a big coincidence for hardware issue to be the cause.

Also no logs, dmesg, etc. showing any issues and no such activities like migration or snapshot backup running. Not even scrub job.

Many Thanks

On 19 April 2018 at 03:52, Ls Cheng <> wrote:

> 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 Fri Apr 20 2018 - 19:27:43 CEST

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