I am seeing the following odd behavior. I have several OSSes, each with a 7T RAID 5.
If I use a single client to create a single 1T file which is striped to a single OST, the performance starts off at about 400 MB/s (which is typical for my HW), then gradually decreases, until it reaches 250 MB/s. I've seen this with both IOZone and dd. As an experiment, I wrote a script that creates two hundred 10G files, without removing them. Again, the performance starts off at 400 MB/s. But, the performance stays nearly the same throughout the test. The only difference between these tests is that in the second case, there are lots of opens & closes, and in the first case, just a single open and close. Can anyone explain what is happening here, and how to possible fix it? Thanks. Roger Spellman Sr. Staff Engineer Terascala, Inc.
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