Re: Latency of "direct path reads"
Date: Mon, 19 Aug 2013 22:38:41 +0100
Message-id: <4A5372D7-DC9C-4E76-BB39-B29629E0E79E_at_me.com>
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
-- http://www.freelists.org/webpage/oracle-lReceived on Mon Aug 19 2013 - 23:38:41 CEST