http://blogs.technet.com/b/timmcmic/archive/2011/07/12/exchange-vss-and-differential-block-size.aspxToday’s backup and restore operations require close coordination between backup applications, the line-of-business application being backed up (for example, Exchange 2010), and the storage management hardware and software. The Volume Shadow Copy Serviceen-USTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)http://blogs.technet.com/b/timmcmic/archive/2011/07/12/exchange-vss-and-differential-block-size.aspx#3467734Mon, 28 Nov 2011 21:44:33 GMTd5e57398-b9ef-4490-9955-07cbb4e4a80d:3467734TIMMCMIC<p>@Andrew:</p> <p>Off the top of my head I do not.</p> <p>TIMMCMIC</p> <div style="clear:both;"></div><img src="http://blogs.technet.com/aggbug.aspx?PostID=3467734" width="1" height="1">http://blogs.technet.com/b/timmcmic/archive/2011/07/12/exchange-vss-and-differential-block-size.aspx#3467732Mon, 28 Nov 2011 21:42:31 GMTd5e57398-b9ef-4490-9955-07cbb4e4a80d:3467732Andrew W. McGregor<p>When I look at the shadow details using diskshadow, I see the following for attributes.</p> <p> - Attributes: &nbsp;No_Auto_Release Persistent Differential</p> <p>Would you know what this means?</p> <div style="clear:both;"></div><img src="http://blogs.technet.com/aggbug.aspx?PostID=3467732" width="1" height="1">http://blogs.technet.com/b/timmcmic/archive/2011/07/12/exchange-vss-and-differential-block-size.aspx#3467728Mon, 28 Nov 2011 21:25:08 GMTd5e57398-b9ef-4490-9955-07cbb4e4a80d:3467728TIMMCMIC<p>@Andrew:</p> <p>Thanks for the detailed question...</p> <p>To my knowledge networker utilizes the default software provider from Microsoft which would subject them to the 16 K limit.</p> <p>After a successful backup has completed to my knowledge the backup application will cleanup the shadows created. &nbsp;This would then reclaim the space.</p> <p>You can see the shadows that you have created / existing by using VSSAdmin list shadows.</p> <p>You can also discard all shadows by running diskshadow (at the command prompt). &nbsp;Then run delete shadows all followed by exit to return to the command prompt.</p> <p>TIMMCMIC</p> <div style="clear:both;"></div><img src="http://blogs.technet.com/aggbug.aspx?PostID=3467728" width="1" height="1">http://blogs.technet.com/b/timmcmic/archive/2011/07/12/exchange-vss-and-differential-block-size.aspx#3467725Mon, 28 Nov 2011 21:20:01 GMTd5e57398-b9ef-4490-9955-07cbb4e4a80d:3467725Andrew W. McGregor<p>Tim,</p> <p>This is very enlightening indeed. I think I see an inefficient block size being used by Networker to back up our Exchange 2010 databases. As I understand it, when writes are made to the database after a volume snapshot has been made, there are original blocks that are written to the differential storage which is located on a disk on the system in which the volume is located. In our case certain disks have been designated as the differential storage areas for other disks where the data volumes are located. Our issue now is that there is a great deal of space being eaten up by the differential data and of course we can&#39;t see it in the form of a file on the disk, but the space is definitely disappearing.</p> <p>Does this sound like something that could be attributed to what you are describing above? I will find out what the block size is that is being used by Networker. Also, looking at the vssadmin output &nbsp;shows that the limit for the storage space is unbounded. I&#39;m also wondering if that needs to be configured so that the space used is not too much. Will that create an issue if the storage space has a limit on it and the differential data goes over that amount?</p> <p>Any help understanding this completely is much appreciated.</p> <p>Thanks,</p> <p>Andrew</p> <div style="clear:both;"></div><img src="http://blogs.technet.com/aggbug.aspx?PostID=3467725" width="1" height="1">