nerdexam
Oracle

1Z0-820 · Question #53

1Z0-820 Question #53: Real Exam Question with Answer & Explanation

The correct answer is D. Put all of the zones in the same ZFS file system and set the dedup property for the file system to on. E. Put each zone in a separate ZFS file system within the same zpool.. Options D and E are correct because ZFS deduplication operates at the pool level - the dedup hash table is shared across all datasets within the same zpool. Setting dedup=on on a ZFS file system (D) or on separate file systems within the same zpool (E) causes ZFS to store only on

Managing Data Storage

Question

You are going to create live zones on you server. Disk space is critical on this server so you need to reduce the amount of disk space required for these zones. Much of the data required for each of these zones is identical, so you want to eliminate the duplicate copies of data and store only data that is unique to each zone. Which two options provide a solution for eliminating the duplicate copies of data that is common between all of these zones?

Options

  • ACreate the zones by using sparse root zones.
  • BSet the dedup property to on and the dedupratio to at least 1.5 for the zpool.
  • CPut all of the zones in the same ZFS file system and set the dedupratio property for the ZFS file system
  • DPut all of the zones in the same ZFS file system and set the dedup property for the file system to on.
  • EPut each zone in a separate ZFS file system within the same zpool.

Explanation

Options D and E are correct because ZFS deduplication operates at the pool level - the dedup hash table is shared across all datasets within the same zpool. Setting dedup=on on a ZFS file system (D) or on separate file systems within the same zpool (E) causes ZFS to store only one copy of any identical data block, regardless of which zone "owns" it. These two options represent different valid configurations: one shared filesystem vs. separate per-zone filesystems - both work because the dedup table is pool-scoped.

Why the distractors are wrong:

  • A (Sparse root zones): This is a Solaris 10 concept where OS directories are loopback-mounted from the global zone - it only covers system directories, not all shared application data, and is not true block-level deduplication.
  • B & C: dedupratio is a read-only reporting property that shows the current deduplication ratio achieved; you cannot set it. Only dedup=on is the writable configuration property.

Memory tip: Think of it this way - dedup is the switch you flip (on/off); dedupratio is the gauge you read afterward. You can't configure a result, only observe it. Any answer that asks you to set dedupratio is immediately wrong.

Topics

#ZFS deduplication#Zone storage optimization#Filesystem management#Copy-on-write

Community Discussion

No community discussion yet for this question.

Sign up to join the discussion
Full 1Z0-820 Practice