Re: Latency of "direct path reads"
Date: Tue, 20 Aug 2013 22:58:52 +0100
Message-ID: <CAGdek=wVedUQmECeo+PrZF=V__Uze0xGuo9vSzuidDM=FuOPdg_at_mail.gmail.com>
Hi Amir,
Are you able to replicate a situation with > 1s for single read ? If yes enable trace on Oracle and
setup a wireshark on dNFS interface. Using a tim from trace you should be able to find corresponding logs from network sniffer and maybe you will find a reason why it take too long.
It could be a network retransmission so your network guys will have to find a root cause or it could be a long read request on EMC so problem will be redirected to storage guys.
Here is a example of output from 10046 trace, strace command and wireshark
http://oracleprof.blogspot.ie/2013/01/how-dnfs-database-clone-works-part-1.html
regards,
Marcin Przepiorowski
On Tue, Aug 20, 2013 at 3:14 AM, Hameed, Amir <Amir.Hameed_at_xerox.com> wrote:
> Hi Austin,
> I really appreciate your feedback. I did go through the document that you
> have mentioned below a few times in the past but most of the patches listed
> at that time were either released for Linux or Exadata for Solaris; we are
> SPARC Solaris. After we provided pstack dumps to Oracle today, Oracle
> confirmed that we are hitting the same bug that you have mentioned below.
> But since we are at 11.2.0.3.6 and the patch for Solaris is available for
> 11.2.0.3.5, Oracle is in the process of back-porting the patch.
>
> You are also right about the 32k chunk size because of the rsize and wsize
> mount options and I confirmed it by running truss. How has your experience
> been with dNFS so far?
>
> Thanks
> -----Original Message-----
> From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org]
> On Behalf Of Austin Hackett
> Sent: Monday, August 19, 2013 5:39 PM
> To: oracle-l digest users
> Subject: Re: Latency of "direct path reads"
>
> Hi Amir
>
> I've recently deployed a 5 node 11.2.0.3.2 RAC with dNFS and a NetApp
> FAS6290 into production.
>
> Are you familiar with MOS Doc ID 1495104.1, which has a list of
> Recommended Patches for Direct NFS? If you don't have these patches
> applied, I would definitely suggest getting them installed. For example,
> during my initial lab tests I kept hitting bug 15987992 under heavy
> sequential read load. I/O would completely hang for a seemingly indefinite
> period. Admittedly, this doesn't sound like what you're seeing. However,
> there are other bugs mentioned which sound like they could be of interest.
> You may need to request back ports of the patches for your exact PSU-level.
> I did.
>
> Apologies if this is old news.
>
> Regarding your question about sending > 32K chunks of data, the Oracle
> recommended value for the rsize mount option is 32K, so I think a 1MB multi
> block read would be split into 32K chunks under KNFS anyway. I don't know
> if DNFS uses a larger transfer buffer size?
>
> Austin
>
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>
-- Marcin Przepiorowski http://oracleprof.blogspot.com -- http://www.freelists.org/webpage/oracle-lReceived on Tue Aug 20 2013 - 23:58:52 CEST