Dell EMC Metro node 7.0.1 Online Help

Guidelines

• When adding metro node to an existing environment, know what your host to storage array (native) performance since although metro node tends to boost read intensive workloads because of additional caching, often times metro node can only perform just as well as this native performance.
• Metro node could simply be the victim of poor storage array performance.
• Unexpectedly low IOPS could indicate array saturation or back-end fabric issues. Recommended to check back-end aborts/retries.
• Keep in mind many things affect storage-array IOPS performance such as:
  • IO request size
  • Read vs. write request
  • Underlying disk type (SSD, FC, SATA)
  • RAID type — 0, 1, 0+1, 5, 6
  • FAST VP — Fully Automated Storage Tiering across 3 distinct tiers: Flash, enterprise hard disk drives (10K and 15K rpm), and high-capacity SATA HDDs
  • Thin/thick pools
  • Storage array cache settings and size
  • Running snapshots/clones
• For arrays with write-back caching, writes will generally be faster than reads. If the read data is cached by the array, then the latency will be comparable to that of the writes.
• Performance can be negatively affected while running snapshots or clones.
• For Symmetrix arrays, performance can be impacted by Write Pending (WP) limits when there is a lack of available free cache slots to accept incoming writes, forcing the array to proactively flush pages to disk. Running SRDF sessions might also affect performance.
• For CLARiiON arrays, performance can be impacted by forced flushes due to the lack of available cache to buffer writes.

Corrective actions

• Check back-end errors: These indicate that metro node had to abort and re-try operations. Could be a back-end fabric or storage-array health issue.
• Examine the back-end fabric for its overall health state, recent changes, reported errors, and properly negotiated speeds.
• Examine the back-end storage array for general health state, and that performance best practices are followed for disk/RAID layout when needed.
• Utilize available performance monitoring tools from the storage array vendor to confirm the array's performance. Additional metrics available to the array but not visible to metro node might shed light on the problem.
• Ensure to run the recommended storage array firmware version. Check for newer software releases and known bug fixes.
• Consult your storage array vendor's performance specialists if the problem persists.

Changing the view

Use the following appropriate selection criteria to filter the data:

• Director — Allows you to select all directors or a specific director in the cluster.
• Read and Write check boxes — Allows you to select one or both check boxes to filter throughput for Reads and Writes.

Viewing the Back-end Throughput chart

1. From the GUI main menu, click Performance.
2. In the Performance Dashboard, select the tab in which you want to display the Back-end Throughput chart (or create a custom tab).
3. Click +Add Content.
4. Click the Back-end Throughput icon.