<p class="MsoNormal">Exchange 2010, which came out of Release Candidate only a few weeks ago, no longer has the single instance storage we've come to know and love for ages. But to help compensate for the additional space required without SIS, the Exchange team compresses the database, as described below.</p>
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<p class="MsoNormal"><span style="font-size: 7pt; color: black;" lang="EN">&quot; </span> <span style="color: black;" lang="EN">In Exchange 2010, the store schema has changed so that all data in a mailbox have stored-in tables close to each other in the database. Actually, each mailbox has its own folder, message header, body, and its own view table. So, the concept of single instance storage no longer exists when it comes to Exchange databases. A side effect of removing SIS from Exchange was that a database was bloated by approximately 20%. Exchange PG found a solution to this by compressing the databases (more specifically message headers and text/HTML bodies). By giving each mailbox its own set of tables, most I/Os performed against a DB are now mostly sequential I/Os.&quot;</span></p>