A Hitachi Dynamic Provisioning pool has exceeded a threshold and the administrator wants to reduce the pool usage below the threshold setting. How would this be achieved?

The correct answer is C. Use Zero Page Reclaim. Zero Page Reclaim (ZPR) is correct because, in thin provisioning, deleting data on the host leaves zeroed pages still allocated in the pool - the array doesn't automatically know they're empty. ZPR scans DP Volumes for pages containing only zeros and returns them to the pool…

Performance Monitoring and Tuning

Question

Options

AExpand pool volumes.
BSet Host Mode option 40.
CUse Zero Page Reclaim.
DShrink some DP Vols.

How the community answered

(20 responses)

A
10% (2)
B
5% (1)
C
85% (17)

Explanation

Zero Page Reclaim (ZPR) is correct because, in thin provisioning, deleting data on the host leaves zeroed pages still allocated in the pool - the array doesn't automatically know they're empty. ZPR scans DP Volumes for pages containing only zeros and returns them to the pool, directly reducing actual pool usage without any capacity changes.

Option A (Expand pool volumes) increases total pool capacity, which lowers the percentage used but doesn't reclaim a single allocated page - it addresses the symptom, not the consumption. Option B (Host Mode option 40) is a host-compatibility flag unrelated to pool space management. Option D (Shrink DP Vols) reduces the virtual size of volumes but cannot reclaim pages that are already allocated in the pool - only unwritten space is affected.

Memory tip: Think of ZPR as a vacuum for your pool - it finds the "hollow" (all-zero) pages left behind after host deletions and sucks them back into the pool. If the data is gone (zeroed), ZPR can reclaim it.

Topics

#Dynamic Provisioning#pool threshold#Zero Page Reclaim#capacity management

Community Discussion

No community discussion yet for this question.

Full HAT-680 Practice