- Understanding the Windows Volume Shadow Copy Service
- Working with the vssadmin Command in Vista
- If It Aint Broke, Dont Fix It!
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Working with the vssadmin Command in Vista
Here’s how to check the amount of space you’ve got tied up in shadow copies on your Vista disk drives. Open a command window, then type the same string shown in Figure 2 on the top line.
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Figure 2 Checking the amount of space taken up in shadow copies.
Here’s how to interpret what you see here:
- Drive D (160GB in putative size, 149GB in binary) has 22.357GB of shadow copy storage allocated. At 15 percent of total disk space, that’s just what default values dictate.
- Drive F (320GB in putative size, 298GB in binary) has 10GB of shadow copy storage allocated. That’s because I reset this number manually after converting this former system disk into a data drive, knowing that even 10GB is an unlikely number for duplicate file copy snapshots.
- Drive C (500GB in putative size, 466GB in binary) has 69.9GB of volume shadow copy storage allocated. Here again, that’s exactly 15 percent of total disk space—just what defaults dictate.
Let’s say you see a number you don’t like, or that evaluates to more than 15 percent of the total drive size—don’t forget to convert putative drive size from decimal to binary when calculating this value. That’s when you can use the vssadmin command to set a hard ceiling on shadow copy storage space allowed. To convert decimal disk sizes to binary, first multiply the number of gigabytes by 1 billion (1 x 109), then divide by 230 (1,073,741,824). Take the value reported for “Maximum Shadow Copy Storage Space” and divide it by the binary number of gigabytes for your drive. The resulting percentage will tell you how much of the total space is allocated to shadow copies.
Figure 3 shows before and after vssadmin list storage commands, where I turned restore points back on for the F: drive between “before” and “after.” Notice that the volume shadow copy service automatically resizes the allocated measurement when shadow copies get turned on.
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Figure 3 Before and after vssadmin commands.
Figure 4 shows the syntax I used to resize the shadow storage allocation for Drive F:, including the help file information for this vssadmin subcommand.
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Figure 4 Resizing the storage allocation.