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SSD - Dynamic disk + span volumes - Is it ok?

post #1 of 3
12/24/11 at 9:46pm
Thread Starter 
Hello,

I recently converted my SSD to a dynamic disk, and then spanned it in to another SSD to increase the entire logical volume size. Just wondering if this is OK? As in, will it reduce life or performance drastically of my SSD drive to the point where I should format and just live with two separate volumes on basic disk. I am thinking the answer is no, but wanted to run it across guys who knew before making assumptions. The main thing that stands out to me now is that the alignment is off on the extended (spanned) logical volume.. I am assuming the span caused this and that it is ok.

Just looking for some re-assurance i guess... Thanks.
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post #2 of 3
8/1/12 at 7:40am
Yes, I have same question here as well. There's next to 0 information on the net regarding dynamic disks, alignment, and SSDs. The alignment is the most glaring issue, as I'm not sure if the offset is correctly reported with dynamic disks. As it stands, if you convert a blank disk to dynamic, then check the offset of that drive's partition/volume, it shows up as misaligned, starting at 32256.

So, to partially appease my mind by having proper alignment, what I did was create a small 1MB volume on the 2nd drive aligning it to 1024, then I did the RETAIN command on it to associate a partition with it, then every subsequent "create volume xxxxx align=1024" created the volume(s) I needed with the correct alignment.

However, it's worth noting that on both of my dynamic disks, the first partitions on each start with an offset of 31K (32256) which isn't properly aligned. If these were basic disks, their offsets would be 1MB (1024576), which is aligned correctly, so I don't know what the hell's going on. Apparently the the small partition in the beginning of dynamic disks, the one with the 31K offset, is for the metadata. Although I can't find a way to fix that, at least the remaining volumes/partitions now have the correct alignment.
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post #3 of 3
8/1/12 at 8:19am
Ok, finally found an article that confirms alignment with dynamic disks is done correctly on Windows 6.x systems (Vista/7/2k8/2k8r2).
Quote:
What this means is that even though the volume will get the desired performance boost, the partition isn’t aligned correctly. But it doesn’t matter since it isn’t the partition we care about, it’s the volume.

However, if we ran the WMIC command now it would tell you that the alignment is NOT correct. This is because the command is checking the PARTITION instead of the VOLUME. And there isn’t a corresponding way to check volume alignment.

In fact ANY utility that is querying the starting point of the partition is going to appear to be wrong. But they aren’t. It just isn’t understood the hair splitting difference between ‘partition’ and ‘volume’.

Now there is still a way to use the DMDIAG tool from Windows 2003 to get the volume information we want. The last version of this tool will display volume information…and it works on Windows 2008 and 2008R2. You’d get an output that would include…

http://blogs.technet.com/b/askcore/archive/2011/09/26/alignment-changes-in-windows-2008-and-2008-r2.aspx
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