D-ISM-FN-23 Sample Questions & Answers

Modern arrays like Dell PowerStore often have built-in migration tools that use storage virtualization. These tools can import LUNs from legacy arrays and perform the data copy in the background while the application remains online. The final cutover involves a brief I/O pause to remap paths, which easily meets the sub-10-minute downtime window. Backup/restore is an offline process with significant downtime. Host-based migration adds overhead to the host and can be complex.

This statement describes the purpose of a backup, not an archive. A backup is used for operational recovery (restoring data after loss or corruption). An archive is used for long-term retention of data that is no longer actively used, typically for compliance, legal, or historical purposes. Retrieval from an archive is generally slower than from a backup.

This is the primary advantage of variable-length block deduplication. Unlike fixed-length, which would see all subsequent blocks as new due to the shift, variable-length deduplication uses a sliding window to find block boundaries based on the data content itself. It will identify that only the beginning of the file has changed and will quickly re-synchronize, recognizing the rest of the file's data as duplicate blocks that already exist on the target. Therefore, only the new data needs to be sent.

A VTL uses disk storage that emulates a tape library. This allows the backup software to write data at high, disk-based speeds, significantly shortening the backup window. The VTL can then de-stage the data to the physical tape library in the background for long-term, low-cost retention. This combines the performance of disk with the economics of tape.

The primary purpose of a failover cluster is to provide high availability. If one server (node) in the cluster fails, the services and applications it was running are automatically and quickly restarted on another healthy node in the cluster. This minimizes downtime and ensures the service remains available to users.

RAID 6 (double parity) is the correct choice as it stripes data and parity across all disks and can withstand the failure of any two drives. With 8 drives, the capacity of two drives is used for parity. Calculation: (8 drives - 2 parity drives) * 4 TB/drive = 24 TB. RAID 10 provides high performance but can only guarantee protection against a single drive failure in each mirrored pair. RAID 5 can only tolerate one drive failure.

Thin provisioning allows administrators to present a logical volume size larger than the physical capacity currently allocated, simplifying management as they don't need to resize volumes frequently. They can manage the overall pool capacity instead.

By allocating physical space only when data is actually written, thin provisioning improves storage efficiency. It avoids having large amounts of allocated but unused space, allowing for better overall utilization of the storage pool (over-subscription).

Network Attached Storage (NAS) is designed for file-level access over a network. It uses standard file sharing protocols like SMB (for Windows/macOS) and NFS (for Linux/Unix) to serve files to multiple clients simultaneously, which is the exact requirement for home directories and departmental shares.

Object storage is ideal for this scenario because it decouples the data (the object) from standard file system constraints. Its flat namespace and use of unique IDs allow for virtually limitless scalability. Crucially, it allows for extensive, customizable metadata to be stored with each object, which is essential for managing and searching billions of items. Access via RESTful APIs (like S3) is the standard for cloud-native applications.

In a write-back cache policy, the primary goal is to improve write performance. The storage system accepts the write data into its fast cache, immediately sends an acknowledgment back to the host, and then writes (de-stages or flushes) the data from the cache to the slower persistent disk storage at a later, more opportune time. This makes the write operation appear very fast to the host.