E20-526 Online Practice Questions and Answers

Correct Answer: D

XtremIO storage is natively thin provisioned, using a small internal block size. This provides fine-grained resolution for the thin provisioned space. All volumes in the system are thin provisioned, meaning that the system consumes capacity only when it is actually needed. XtremIO determines where to place the unique data blocks physically inside the cluster after it calculates their fingerprint IDs. Therefore, it never preallocates or thick-provisions storage space before writing.

References: Introduction to the EMC XtremIO STORAGE ARRAY (April 2015), page 22

Correct Answer: D

Architecting a database on an All Flash Array (AFA) like EMC's XtremIO is best done by reviewing practices to optimize I/O performance. One consideration is the use of Advanced Format and how it impacts the performance of the database Redo logs. Advanced Format refers to a new physical sector size of 4096 bytes (4KB) replacing original 512 byte standard.

References: https://community.emc.com/community/connect/everything_oracle/blog/2014/07/18/xtremiobest-practices-advanced-format-512e-and-native-modes

Correct Answer: C

XtremIO clusters with 60 TB of physical usable flash capacity can now logically support 360 TB or more of capacity at typical 6:1 data reduction (deduplication plus compression) ratios. Here we have a 4:1 reduction ratio, so 25 TB would be enough. The 250,000 IOP requirments indicates that we need at least two Bricks.

References: https://store.emc.com/en-us/Product-Family/EMC-XtremIO-Products/EMC-XtremIO-All-FlashScale-Out-Array/p/EMC-XtremIO-Flash-Scale-Out

Correct Answer: C

Per IDC's best practices the toolkit fills the array 2x.

References: https://community.emc.com/docs/DOC-35014

Correct Answer: D

The workflow for refreshing XtremIO Snapshots, containing Oracle Database files, consists of the following five simple steps:

1.

Shut down the database instances with files in the target Snapshot Set.

2.

Dismount the ASM disk group (or file systems) involved.

3.

Refresh the Snapshot via XtremIO GUI (or CLI or RESTful API).

4.

Mount the ASM disk groups (or file system) involved.

5.

Start the database instances.

This entire workflow is measured in seconds (not minutes).

Incorrect Answers:

A: The refresh command is a powerful tool for test and development environments and for the offline processing use case. With a single command, a snapshot of the production volume or CG is taken and the SCSI face of the volume, which was mapped to the test and development application, is moved to it. This allows the test and development application to work on current data without the need to copy data or to rescan.

References: https://www.emc.com/collateral/white-papers/h14485-xtremio-snapshot-refresh-oracledatabases.pdf, page 8

Correct Answer: D

Any copy in the hierarchy tree can be deleted without effecting the parents or children.

Incorrect Answers: B: Deleting a snapshot in the middle of the tree triggers an asynchronous process. This process merges the metadata of the deleted entity's children with that of their grandparents. This ensures that the tree structure is not fragmented.

C: It is possible to create copies of the production volumes in order to protect against logical data corruption. Multiple copies can be created over a short interval in order to provide a fine RecoverPoint Objective (RPO) in a cyclic manner (a superior RPO to a backup).

References: https://www.emc.com/collateral/white-paper/h13035-wp-introduction-to-xtremiosnapshots.pdf, page 14

Correct Answer: A

Correct Answer: C

Oracle Database performs I/O on data files in multiples of the database block size (db_block_size), which is 8KB by default. The default Oracle Database block size is optimal on XtremIO. XtremIO supports larger block sizes as well. In the case of multiblock I/O (e.g., table/index scans with access method full), one should tune the Oracle Database initialization parameter db_file_multiblock_read_count to limit the requests to 128KB. Therefore, the formula for db_file_multiblock_read_count is: db_file_multiblock_read_count = 128KB / db_block_size

In our case the block size is 1 MB, so the formula db_file_multiblock_read_count is 1 MB/ 8KB = 1024/8 = 128

References: https://www.emc.com/collateral/white-papers/h13497-oracle-best-practices-xtremio-wp.pdf, page 21

Correct Answer: A

Storage capacity and performance scale linearly, such that two X-Bricks supply twice the IOPS, four X-Bricks supply four times the IOPS, six X-Bricks supply six times the IOPS and eight X-Bricks supply eight times the IOPS of the single X- Brick configuration. However, the latency remains consistently low (less than 1ms) as the system scales out. The sub-millisecond latency is validated by actual test results, and is determined according to the worst-case scenario.

References: Introduction to the EMC XtremIO STORAGE ARRAY (April 2015), page 37

Correct Answer: B

With VMware ESX 5.5, the VMware hypervisor cannot work with LUNs that use a logical block size of 4K. When using VMware, be sure to specify Normal (512 LBs) from your XtremIO array.

References: https://gruffdba.wordpress.com/2015/08/02/4k-logical-block-size-size-fails-on-vmware/