note
radiantmatrix
<p><em>they are both exactly the same thing, a series of blocks on a disk. The fact that you might have to do one extra lookup to find out where those blocks reside is fairly meaningless in the real world.</em>
<p>That's simply not true of DMGs. It's a lot more than an extra lookup, and it's a heck of a lot more complex to mount what's essentially a (non-journaling) loopback filesystem with extra integrity features than it is to add LVM or RAID.
<p>For user data, a DMG mounted from a local disk is going to be quite fast enough -- the difference in performance between that and a standard local volume is going to be smaller than the difference between a local volume and one mounted via AFP (or even USB). For thinks like the swap volume, temporary file space, parts of /var, etc., the overhead of the DMG driver would make a noticeable performance impact.
<p><em>From the point of view of both the operating system and the data contained on the disk, there is no difference between a filesystem on a physical disk and a filesystem on a disk image.</em>
<p>That's simply not true. There's no raw block device with a DMG. If your underlying filesystem is damaged in such a way that the DMG integrity is compromised, the DMG becomes unmountable. Because of the lack of a block device associated with a DMG, you can't use generalized disk-recovery tools.
<p>Now, none of that should prevent someone from using a DMG to store data -- and I never said it should. However, the performance and reliability concerns do make a compelling argument against using a DMG to store the OS's support system and kitchen sink.
<!--
<p><small><b>Updates:</b><ul type='square'>
<li>date : desc</li>
</ul></small></p>
-->
<div class="pmsig"><div class="pmsig-375088">
<small>
<small><font color='#000000'><</font><font color='#1a1a1a'>–</font><font color='#343434'>r</font><font color='#4e4e4e'>a</font><font color='#686868'>d</font><font color='#828282'>i</font><font color='#9c9c9c'>a</font><font color='#b6b6b6'>n</font><font color='#d0d0d0'>t</font><font color='#eaeaea'>.</font><font color='#d0d0d0'>m</font><font color='#b6b6b6'>a</font><font color='#9c9c9c'>t</font><font color='#828282'>r</font><font color='#686868'>i</font><font color='#4e4e4e'>x</font><font color='#343434'>–</font><font color='#1a1a1a'>></font></small>
<!--<-</small><b>radiant</b>.<b>matrix</b><small>-></small-->
<br><a href='http://radiantmatrix.org/'>Ramblings and references</a>
<br><em>The Code that can be seen is not the true Code</em>
<br><em>I haven't found a problem yet that can't be solved by a well-placed [http://en.wikipedia.org/wiki/Trebuchet|trebuchet]</em>
</small>
</div></div>
679342
680163