Storage Networking Host Access Best Practices
Storage Networking Host Access Best Practices
The Storage Networking (SNW) Host Access feature allows you to define which host can see and access specific drive and medium changer devices within the tape library. The SNW feature is a licensed feature that is sold on a per drive quantity basis. Once the SNW license is applied to the library you must assign a SNW license to specific drives that you would like to leverage the SNW features on. When the SNW license is applied to the drive then you can perform all SNW features with that drive. Even though you can license an individual drive within a multi-drive library it is rare that you wouldn’t simply license all drives so you can leverage the SNW features on all of the drives. One thing to consider is that when you apply a SNW license to a drive it’s SAN/Host access presentation is removed until the drive is defined within an Access Group. The SNW Host Access feature can be leveraged with LTO-5 and above drives. It is also required that all SNW enabled drives be connected to an Ethernet Expansion Blade (EEB).
The first step in leveraging the SNW Host Access feature is to define information about each host. This requires that the Host(s) are already zoned or direct attached to the drive(s). When the drives are properly zoned or direct attached to the host(s) then a listing of “Unknown” host devices will be displayed in the Host Configuration screen based on their WWPN seen by the drive(s). It is not required to define the details about each host in the Host Configuration screen but doing so will make it easier to differentiate one host from the next. Giving the host a specific name and operating system type will make it much easier to understand which host it is so you can assign its device access later.
The second step in the process is to define an Access Group. An Access Group is a collection of one or more hosts that will need to access the same pool of drive or medium changer devices. You can make a single Access Group for each Host or you can make a single Access Group that contains all of your hosts. How you define the Access Groups depends on how you want your hosts to see the devices. Listed below are a couple of Access Group Examples.
The library is configured with a single partition that contains 10 drives. There is one master server and two media servers. You want the master server to see the medium changer and all of the drives and then you want each media server to only see 5 of the 10 drives. In this scenario you would need to create three separate Access Groups. The first Access Group would be for the Master server and it would contain all of the library devices (Medium Changer + 10 drives). The second Access Group would be for the first media server and contain Drives 1 – 5. Then the third Access Group would be for the second media server and contain Drives 6 – 10.
The library is configured with a single partition that contains 10 drives. There is one master server and two media servers. You want the Master and Media servers to see all of the same devices. In this scenario you would create one Access Group that contains the three hosts (Master, Media 1 & Media 2). The Access Group would then contain the medium changer and all 10 drives.
Being able to group multiple hosts together in the same Access Group minimizes the complexity and repetitiveness needed if you could only configure device access on a per host basis. One restriction of the Access Group feature is that any Host can only belong to one Access Group at a time. Even though you can share devices between Access Groups you cannot share hosts between Access Groups.
Another important factor to consider is that the Access Group Host Access feature does not validate your host connectivity or zoning in a multi host environment. Once one host is zoned to all devices the Access Group feature will allow you to assign device access to any other host that may have partial zoning. The only requirement is that each host be zoned to at least one drive so it can be seen by the library and listed in the Host list. If a host is displayed in the host list you can assign it to an Access Group. Just because a host is assigned to an Access Group and that Access Group is mapped to a specific group of devices does not automatically “Fix” zoning limitations or issues. The SAN administrator still needs to verify that the proper host to drive zoning is defined and deployed.
Each of the Quantum Tape Libraries that support the SNW Access Group feature has slightly different GUI formats when configuring the SNW features. Please reference the User’s Guide for the specific Quantum Tape Library you are working with for complete details on working with the SNW feature.