Finding Buffer Credit Issues

 

Buffer credit issues are typically caused by discrepancies in the I/O workload capabilities of an initiator or target. Usually the targets are the storage systems, and they are extremely fast, and often times the initiators are hosts that may be fast but are oversubscribed or have saturation or contention issues. This video demonstrates how to identify these issues.

Find the Root Cause of Buffer-to-Buffer Credit Shortages

A significant amount of buffer credits would be more than 20,000 or 30,000 buffer credit shortages per second. Oftentimes when we see this on ISL’s, the ISL’s are on the same switch, and oftentimes the shortages are caused by the same issue if they’re on the same switch.

An important thing to look for when we see buffer credit shortages is SAN Port Transmit patterns: transmit on the fabric and on the VMware systems, to see where the issues are. We usually don’t see the F ports or the initiator or target ports showing the buffer credit issues, but we do usually see some pattern that matches the buffer credit shortages on one of the F ports.

Additionally, we look at the VMware read throughput for a host that matches the buffer credit issue pattern exactly. And looking at the VMware guest, it runs on an ESX host, where we can see a significant imbalance in the port traffic. So, there’s an issue here where we have a host that is reading data off of the storage and fabric, but it’s not able to read it as fast as it’s being sent, and so there are some delays with the buffer credit shortages. We also see an imbalance in terms of the host activity on its two paths.

Troubleshoot and Resolve Buffer Credit Issues

There are a couple ways to resolve this. Ideally, we’d like to have traffic evenly going across the two different ports, and that can be done with Active-Active configurations, or by having multiple data stores that are hosting the active data and assigning those data stores to different physical paths. By balancing things better in the environment, you should be able to resolve the buffer credit shortages.

If that doesn’t resolve the issue, you need to look at the different speeds and feeds on the wire, and it may be a situation in which you have to upgrade the host port to a higher speed.

IntelliMagic Vision has reports that easily detect buffer credit issues. If you would like to discuss buffer credit shortages or issues in your environment with an IntelliMagic expert, feel free to reach out to reach out to us at info@intellimagic.com or contact us here.

Related

Video

Improve Collaboration and Reporting with a Single View for Multi-Vendor Storage Performance

Learn how utilizing a single pane of glass for multi-vendor storage reporting and analysis improves not only the effectiveness of your reporting, but also the collaboration amongst team members and departments.

Watch video
Video

A Single View for Managing Multi-Vendor SAN Infrastructure

Managing a SAN environment with a mix of storage vendors is always challenging because you have to rely on multiple tools to keep storage devices and systems functioning like they should.

Watch video
Blog

Cleaning up the SAN Fabric: Getting Your House in Order Part Two

Cleaning up SAN fabric zones and storage array masking views are often a forgotten part of good storage hygiene. Although unused zones and masking views may seem harmless, they pose an availability risk to your environment on multiple fronts.

Read more

Go to Resources

Request a Trial or Demo

Whether you’re in the early stages of product research, evaluating competitive solutions, or trying to solve a problem, we’re happy to help you get the information you need to move forward with your IT initiatives.

Discover End-to-End SAN Performance, Capacity, and Configuration Monitoring

IntelliMagic Vision for SAN

End-to-End SAN Performance, Capacity, and Configuration Monitoring

Learn More

IBM Spectrum Virtualize, SVC

Performance Management for IBM Spectrum Virtualize, SVC and Storwize

Learn More

Dell EMC Unity

Performance Management for Dell EMC Unity

Learn More

HPE 3PAR

Performance Management for HPE 3PAR StoreServ Storage

Learn More

Dell EMC XtremIO

Performance Management for Dell EMC XtremIO

Learn More

SAN Fabric

Unified SAN Fabric Performance Management

Learn More

Show all

Flexible Deployment and Monitoring

On Premise

Install the software on premise and use it offline

In the Cloud

The Cloud based deployment can be accessed from everywhere in the world and is easy to share with colleagues,

Add On Services

Get help with the deployment and the management of the software