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|Provisioning best practices|
You'll also need to think about replication early on in the cycle. "When it comes to provisioning for replication, you have two options--but a lot depends on the manufacturer," says Arland. You can define the replication during the initial provisioning when you'll pair drives for replication. Some midrange arrays, how-ever, allow for more flexibility by letting you specify replication at a later time. "The best practice would be to take care of the replication during the initial provisioning," he adds.
GlassHouse's Weinstein recommends that snapshot and replication be decided even earlier, when you're gathering the initial requirements. "There is only so much capacity available for internal snapshots, so you need to plan for it during the design phase," he says.
Zoning and masking don't require much planning. "Zoning and masking can be done before or after the provisioning or in parallel," says Datalink's Anderson. The only decision is whether to do hard or soft zoning. Hard zoning uses the physical port on the switch. Soft zoning relies on the device's worldwide name, a 16-character string. "The trend today is to use the name. Management tools and switch vendors prefer worldwide name-level zoning," says Anderson.
Carving up the storage
It's only after they have captured the storage service requirements that the pros start carving the physical array into logical chunks of storage. This entails firing up the storage array vendor's element manager, a low-level tool.
In the past, provisioning was done strictly through the command line interface (CLI). When mastered, the CLI gave very granular control and was fast. In recent years, vendors have offered GUI element managers that rival the CLI for control. Third-party tools have also emerged, but they have been slower to catch on.
GUI-based element managers are easier. "We're new at this. We got a new array earlier this year so we're using the GUI," says Anthony Bergen, manager of server technologies at The North West Company Inc., a retail distributor based in Winnipeg, Manitoba. The company is using the Navisphere element manager that came with its Dell Inc./EMC Corp. array.
Bergen is using Dell consultants to set up the initial provisioning on The North West Company's new array. The consultants configured the storage into striped meta LUNs, 300GB in size. Meta LUNs are created by striping across multiple storage volumes to create new, larger volumes. In the case of The North West Company, the meta LUNs are formed out of 50GB LUNs. "Meta LUNs allow us to grow our storage easily," says Bergen.
Meta LUNs are similar to concatenated LUNs. In both cases, multiple, smaller LUNs are joined to form a large LUN. Meta LUNs, however, are striped across all the spindles of the constituent LUNs, which results in better performance. With concatenated LUNs, data is written to each LUN sequentially, filling the first constituent LUN before moving on to the next, according to GlassHouse's Weinstein. Meta LUNs and concatenated LUNs are particularly useful when the organization wants to expand existing volumes on the fly.
The final provisioning step entails setting the masking to ensure that only the right servers see the newly provisioned LUNs. System admins can then use the volume managers on the servers to find the storage.
This was first published in October 2006