The formatting progress on Windows server 2012 is too slow for the thin LUNs from Oceanstor 18500

Publication Date:  2015-12-15 Views:  832 Downloads:  0
Issue Description

The thin LUN was mapped to the Windows server 2012, it was fast to format the LUN in the first time, but it was very slow to re-format it in second time. When turning on the performance monitoring tool, we can see the duration and bandwidth as below:

for the first time, it finished within 5 minutes; but for the second time, it took about 20 hours.

Alarm Information

None

Handling Process

1. With the performance data from the storage, we can see the bandwidth is about 360MBps when formatting the 32TB LUN, the whole formatting progress last for about 20 hours. Due to the large amount of IOs, the “quick format” is just not like a real quick format for the storage.

2. We checked this problem with Microsoft, when formatting the thin LUN for the second time, there will be extra operation, such as "UNMAP" command, to start the space reclaimation.

Root Cause
When performing the formatting operation for the thin LUN with old data on windows, the OS will send command “UNMAP” to storage to release the storage space, which mean that the OS will write “0” on all the used space, that’s why we see the large bandwidth in the performance data
Solution
 To avoid this issue, we suggest you can disable the function on Windows before you want to format the storage with old data, after the formatting is finished, you can enable it again.

To disable the function:

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To enable the function:

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Suggestions
None

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