IBM Corp. Confirms Shark Features

LastWednesday’s story, “IBMAdds Enterprise Features to Shark,” generated a fair amount of readerfeedback. Enterprise Systems contacted IBM for clarification, andconfirmed the story is accurate, but clarified the concerns of a few readers.

One reader asked how the CUIR feature affects Unixsystems, while another reader worried that the volume sizes we reportedwere too small. Below is IBM’s response to reader concerns:

When we areservicing a Shark in anyenvironment, situations may arise where we need to take a connection to aserver offline.  CUIR automates thisprocess for zSeries servers and--as you said in your article--eliminates manualintervention in this case, which helps to reduce errors and so improves systemavailability.  Only IBM's ESS offersthis function.  During service, we mayalso need to take attachments to open systems servers (using Fibre Channel orSCSI) offline.  In those cases, we donot yet have a CUIR-like function and so manual coordination between the IBMengineer and the staff responsible for the open systems servers would still berequired, as it used to be with zSeries. Your reader spoke about an array being serviced: we do not need to takehost connections (ESCON, FICON, SCSI or Fibre Channel) offline to service anarray.  We need to take host connectionsoffline when servicing that portion of the Shark box where the host adaptersare connected.  And we never take themALL offline at once so if a user configures redundant paths, they'll alwayshave access to their data even when we are servicing the box and even when we areservicing the host adapters.

As yourreader says, for open systems servers Shark supports LUN sizes up to around210GB.  For zSeries (mainframe) servers,the maximum logical volume size we supported was about 9GB (3390-9 volumes).  That limit was largely imposed by the hostsoftware, although it was also built into Shark.  With a combination of host software (OS/390, z/OS, and z/VM) andShark changes, we can now support zSeries (mainframe) volumes with up to 32,760"cylinders", which is approximately 27GB.  Your article correctly identified the benefits fo this change inmaximum zSeries (mainframe) volume sizes. Again, 27GB zSeries (mainframe) volumes are an IBM exclusive with Shark.

Chris Saul

Shark OEMMarketing Programs Manager - IBM Storage Systems Group Disk Systems Marketing