RE: How to flush the writing cache before a test with read

["Jenkins, Lee (ISS Houston)" <Lee.Jenkins@xxxxxx>]

The safest and least test-intrusive way is to calculate the flush time ahead of time and insert the appropriate wait time into the test. I encountered the same issue when testing RAID volumes attached to (shameless plug) HP Smart Array controllers with battery-backed write cache. When the cache (512MB at max config) was filled with random write data it could take a long time for the flush to complete. It was the only way to ensure that the subsequent read-only test data was accurate.

-----Original Message-----
From: fio-owner@xxxxxxxxxxxxxxx [mailto:fio-owner@xxxxxxxxxxxxxxx] On Behalf Of Dan Le
Sent: Thursday, November 18, 2010 3:13 PM
To: fio@xxxxxxxxxxxxxxx
Subject: How to flush the writing cache before a test with read

Greetings,

FIO needs to write data files in order to read them. Without disabling
the write-cache of the disk, I was wondering if there's a way to flush
these data cache to disk right before FIO starts to read these files.

I don't want to run every second "sync && echo 3 >
/proc/sys/vm/drop_caches" at the same time with FIO because of its
incurred overhead. Please help.

Thank you,

Dan
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