I have been doing disk i/o performance testing between iscsi initiater(centos) and iscsi target(netbsd). In the scenerio, I want all the buffers and caches to be disabled (like network buffer, hardware cache). Is there any tool or command to check the disk i/o performance with all buffers and caches disabled and how can I disable these buffers and caches?
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What exactly are you trying to measure, and where? Buffers and caches are designed into the data paths you're using, and are an inherent part of their performance profile. You may be able to disable caching in the disks at each end, but that would probably only be useful if you're trying to measure the basic rates at which you can read/write to the spinning platters, and not of much interest in the total iSCSI system view. You may also be able to control the amount of network buffers allocated to your connections, and by varying them be able to determine their affect on your transfers. – Greg A. Woods May 29 '15 at 21:37
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On the initiator side, use fio (https://github.com/axboe/fio) with direct async I/O to do the testing. This effectively takes the kernel buffer cache out of the picture. – Mike Andrews Jun 01 '15 at 18:48