BAARF – Battle Against any Raid Five
In the chart below, 1 represents good and 5 represents bad.
chart from Cary Millsap:
http://method-r.com/downloads/doc_details/15-configuring-oracle-server-for-vldb-cary-millsap Raid 5 runs into read performance issues in a mixed workload because every write takes two reads plus a write. These two reads can conflict with other readers. Also because Raid 5 is typically configured with small stripe sizes, say 32K or 64K, to mitigate write penalties, a multiblock read can easily span several disks, increasing the chances of concurrency read conflicts.
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