Inside Storage Networking

I recently worked with a customer who had their SAN implemented as depicted in the diagram for a Hyperswap V7000 cluster.   An SVC or FlashSystem cluster that is configured for Hyperswap has half of the nodes at one site, and half of the nodes at the other site.  The I/O groups are configured so that nodes at each site are in the same I/O group.  In the example from the diagram, the nodes at Site 1 were in one I/O group, the nodes at the other were in another I/O group.  A stretched cluster also has the nodes in a cluster at two sites, however each I/O group is made up of nodes from each site.  So for our diagram below,  in a Stretched configuration, a node from Site 1 and a node from Site 2 would be in an I/O Group.   From the diagram we see that each site had two V7000 nodes.  Each node had connections to two switches at each site.  The switches were connected as pictured in the diagram to create two redundant fabrics that s...

Zoning Basics Before I talk about some zoning best-practices, I should explain two different types of zoning and how they work.  There are two types of zoning:  WWPN Zoning and Switch-Port Zoning World-wide Port Name (WWPN) Zoning WWPN zoning is also called "soft" zoning and is based off the WWPN that is assigned to a specific port on a fibre-channel adapter.  The WWPN serves a similar function as a MAC address does on an ethernet adapter.  WWPN-based zoning uses the WWPN of devices logged into the fabric to determine which device can connect to which other devices.  Most fabrics are zoned using WWPN zoning.  It is more flexible than switch-port zoning - a device can be plugged in anywhere on the SAN (with some caveats beyond the scope of this blog post) and the device can connect to the other devices it is zoned to.    It has one distinct advantage over Switch-Port based zoning, which is that zoning can always be specified on a single WW...

IBM Storage Insights was updated recently.  Two new Dashboards that were added are the Advisor Dashboard and the Notifications Dashboard.  IBM Storage Support can see the events in these dashboards. In some cases, it allows Support to more quickly identify problems or other issues that need to be addressed.   Like all tables in Storage Insights, both the Advisor and Notifications Dashboard can be filtered and sorted.  You can also export to PDF, CSV or HTML so that you can do additional sorting, filtering or share items in each of the tables. The Advisor Dashboard The Advisor Dashboard is found under the Insights menu.  This dashboard lists recommendations for changes that you can make to improve the stability of your managed IBM Storage systems.  The recommendations include configuration changes, firmware upgrades, and other changes to enhance the stability and performance of your IBM Storage.     Below you see a capture o...

I was at a recent TechU event and had a discussion with a customer about using IBM Storage Insights to monitor host path count.  More specifically, the customer had a recent outage of a few hosts after doing some maintenance work on some storage and the affected hosts were not connected on all the expected paths.    There are options for using the storage data collections to review host connections. For instance, you could write a script that compares the SVC/Storwize host WWPN definitions to the connected devices to see if any WWPNs are not connected to the SVC.  However, it is much more straightforward to configure an alert in IBM Storage Insights Pro.   Alert Policies were previously covered in these two videos:  You can create an Alert Policy for an agentless host and then configure an alert to notify you when the path count changes.  You would need to create separate policies for each operating system, but after you create the fir...

Troubleshooting CRC Errors On Fibre-channel Fabrics There is no "Easy Button" for troubleshooting CRC errors. It is an iterative process. You make a change, you monitor your fabric, and if necessary you make more changes until the issues are resolved. I frequently have customers who want it to be a one step process. It can be, but usually takes multiple steps. Having said that, before we can fix them, we need to know what CRC errors are and why they occur. What Are CRC Errors? When Do they Occur? The simple answer is that CRC errors are damaged frames. The more complicated answer is that before a fibre-channel frame is sent, some math is done. The answer is added to the frame footer. When the receiver gets the frame, the receiver repeats the math. If the receiver gets a different answer then what's recorded in the frame, then the frame was changed in flight. This is a CRC error. The only time these happen is if the physical plant - cabling, SFPs is somehow...

IBM released a new Alert Policies feature for IBM Storage Insights Pro the first week of March 2019.    John Langlois does an excellent job introducing the new feature here: There are a few more advanced aspects of alert policies that John did not cover.    First, you can add and remove managed storage from Alert Policies from the Alerts Definitions of the storage system that you want to modify.  The following video shows how to do this. Second,  you must remember that if you add storage that has never been in an Alert Policy to an Alert Policy,  any existing alerts defined on that storage are lost and cannot be retrieved.  The following video shows an example managing of this and shows a workaround to preserve those alerts if you want to re-apply them at some point in the future.  

Cisco released a feature in NX-OS v8.3.1 called Automatic Zoning.  The feature does exactly what the name suggests:  it automatically configures zoning for the devices on your SAN.  You can see a video on the feature here: What Is Zoning? SAN (Storage Area Network) zoning is specifying which devices on the SAN  can communicate with which other devices.  Devices are added to a zone.  A zone is a group of devices that can communicate.  Zones are then added to a zoneset.  The zoneset is then activated - this is the configuration that is in effect. There can be multiple zonesets but only one active one at any given time.   By default, any device not zoned (not a member of a zone) cannot communicate with any other device.  A device that is in at least one zone is considered zoned.   Effective zoning prevents unauthorized devices from talking to each other, and minimizes disruptions on the SAN if a device misbehaves....