Showing posts from July, 2022

Troubleshooting Slow Drain Devices on Broadcom Switches

  Slow drain devices are one of the more common problems on storage networks.  They can occur for a variety of reasons.  For a refresher on how they can affect your storage network you should watch  this video .    In this blog post I will go through the basic steps to troubleshoot a slow drain device on a Broadcom fabric.    I will be using command line output from switches.  The CLI format lends itself better to a blog post more readily than screen shots from a GUI, and the commands are consistent across different versions of FOS.    SANnav is a huge change from Brocade or IBM Network Advisor and the screens would look quite different between the two. The first command we will be using is porterrshow.    The above output has been truncated for the ports we are interested in. The counters of interest are in the c3timeout column.  You can see that there are 2 sub-columns, 'tx and 'rx'.   'tx' means the switch is trying to send frames to the device attached to that p

Spectrum Virtualize NPIV and Host Connectivity

 A while ago I wrote  this post  as an introduction to the Spectrum Virtualize NPIV feature.  In this follow-up post I thought I would focus more on host connectivity and the effects of NPIV.    You can watch a quick review of the NPIV feature in this IBM Systems Rockstar video:      NPIV has 3 modes: 1.  Disabled - this mode means that hosts cannot connect to the virtual World Wide Port Names  (WWPNs) on the Spectrum Virtualize cluster, regardless of the fabric zoning 2.  Transitional - this mode means hosts can connect to either the physical or virtual WWPNs on the cluster.  If a host is zoned to both, it will connect to both.   Transitional mode is meant to only be used while you are migrating to NPIV mode and rezoning your hosts to the virtual WWPNs.  It is not meant to be used permanently or even long-term.   3.  Enabled - this means hosts can only connect to the virtual WWPNs.  If they are zoned to the physical WWPNs the connection will be listed as 'blocked' in the devic