Re: EMC Storage Array Issue

From: George Schlossnagle <george_at_omniti.com>
Date: Mon, 15 Apr 2002 11:28:25 -0800
Message-ID: <F001.00444AD8.20020415112825@fatcity.com>

On Monday, April 15, 2002, at 02:08 PM, Anjo Kolk wrote:

> Claudio,
>
> All writes in Oracle are synchronous, they are just fired
> asynchronously. So
> even the DBWR writes synchronously.

My dbw uses asynchronous writes.... I'm writing to qio files, which means that they bypass buffer cache, but I think it's misleading to call those 'synchronous writes', they're asynchronous, unbuffered writes.

14:28:09(george_at_core-0)[~]> truss -tkaio -twrite -tread -p `ps -ef | grep dbw | grep -v grep | awk '{print $2}'`

kaio(AIOWRITE, 396, 0xB0258000, 8192, 0x4FBF6000, 0x01974EC8) = 0
kaio(AIOWRITE, 308, 0xB6BFE000, 8192, 0x48478000, 0x01B20518) = 0
kaio(AIOWRITE, 396, 0xB921A000, 8192, 0x249E8000, 0x019C5558) = 0
kaio(AIOWRITE, 396, 0xB4584000, 8192, 0x24F7E000, 0x0196CA84) = 0
kaio(AIOWRITE, 396, 0xB82BC000, 8192, 0x6D822000, 0x01B543CC) = 0
kaio(AIOWRITE, 313, 0xB5ED4000, 8192, 0x1FCD2000, 0x019EE1D8) = 0
kaio(AIOWRITE, 395, 0xBF256000, 8192, 0x21AE6000, 0x01971958) = 0
kaio(AIOWRITE, 313, 0xB1700000, 8192, 0x1FCD4000, 0x019B65D0) = 0
kaio(AIOWRITE, 396, 0xBA238000, 8192, 0x24F86000, 0x01B5E32C) = 0

....

> So individual writes are synchronously, they are just fired off
> asynchronously.
>
> Anjo Kolk.
>
> claudio cutelli wrote:
>
>> Hi,
>> which background process had the problem?
>> because if lgwr, it already write in sync mode ...
>>
>> ----- Original Message -----
>> To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
>> Sent: Monday, April 15, 2002 5:33 PM
>>
>>> We have implemented a Sun Solaris Cluster (4 machines), connected
>>> to
>>> an EMC storage array. The migration began last fall, and we now have
>>> 15
>>> Oracle instances, with a mixture of 8.1.6 and 8.1.7, located there.
>>> We
>>> recently have had 2 occurances of asynchronous I/O wait times
>>> exceeded.
>>> When this occurs, every database crashes at the same time. The
>>> solution
>>> from EMC is to turn asynchronous I/O off in all of the Oracle
>>> instances
>>> (disk_async_io = false) and to increase the database writer slaves
>>> (dbwr_io_slaves = <something not 0>) to emulate asynchronous I/O.
>>> Has anyone run into this problem before? If so, how did you
>>> "correct" it? My feeling is that EMC is trying to give us a bandage
>>> to
>>> cover up the real problem, by trying to get Oracle to ignore it.
>>>
>>> Thank you.
>>>
>>> --
>>> Scott Canaan (srcdco_at_rit.edu)
>>> (585) 475-7886
>>> "Life is like a sewer, what you get out of it depends on what you put
>>> into it" - Tom Lehrer
>>>
>>>
>>> --
>>> Please see the official ORACLE-L FAQ: http://www.orafaq.com
>>> --
>>> Author: Scott Canaan
>>> INET: srcdco_at_ritvax.rit.edu
>>>
>>> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
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>> --
>> Please see the official ORACLE-L FAQ: http://www.orafaq.com
>> --
>> Author: claudio cutelli
>> INET: c_cutelli_at_hotmail.com
>>
>> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
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>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Anjo Kolk
> INET: anjo_at_oraperf.com
>
> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
> San Diego, California -- Public Internet access / Mailing Lists
> --------------------------------------------------------------------
> To REMOVE yourself from this mailing list, send an E-Mail message
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>

// George Schlossnagle
// Principal Consultant
// OmniTI, Inc 		http://www.omniti.com
// (c) 301.343.6422   (e) george_at_omniti.com
// 1024D/1100A5A0  1370 F70A 9365 96C9 2F5E 56C2 B2B9 262F 1100 A5A0

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Received on Mon Apr 15 2002 - 14:28:25 CDT