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Hi All, Is there a way to tune the zfs prefetch on a per pool basis? I have a customer that is seeing slow performance on a pool the contains multiple tablespaces from an Oracle database, looking at the LUNs associated to that pool they are constantly at 80% - 100% busy. Looking at the output from arcstat for the miss % on data, prefetch and metadata we are getting around 5 - 10 % on data, 50 - 70 % on prefetch and 0% on metadata. I am thinking that the majority of the prefetch misses are due to the tablespace data files. The configuration of the system is as follows Sun Fire X4600 M2 8 x 2.3 GHz Quad Core Processor, 256GB Memory Solaris 10 Update 7 ZFS Arc cache max set to 85GB 4 Zpools configured from a 6540 Storage array
I think that the prefetch will be useful on the apps and backup pools, however I think that on the data and logs pools this could be causing issues with the amount of IO that is being caused by the prefetch and the amount that it is missing in the arcstats could be the reason why the devices are at 100% busy. Is there a way to turn the prefetch off for just a single pool? Also is this something that can be done online or will it require a reboot to put into effect. Thanks in advance for your assistance in this matter. Regards Tony --
 Tony Marshall | Technical Architect Phone: +44 118 924 9516 | | | Mobile: +44 7765 898570 Oracle Remote Operations Management United Kingdom ORACLE Corporation UK Ltd is a company incorporated in England & Wales | Company Reg. No. 1782505 | Reg. office: Oracle Parkway, Thames Valley Park, Reading RG6 1RA 
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