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SAN Virtualization and SAN Storage Consolidation
Out of capacity: What now?
By Greg Schulz
What you will learn from this tip: This tip discusses how to avoid running out of storage capacity by evaluating your options, investigating re-allocation and knowing where to turn if you can't solve the problem yourself.
Running out of storage capacity is similar to running out of gas in your car -- both are impacted by usage and are caused by ignoring indicators and gauges.
Storage and performance thresholds and monitoring tools are equivalent to your cars' dashboard indicator lights. If you ignore them long enough you'll find yourself running on borrowed time and risk running out of resources and being stranded. Unlike your car where you can call AAA for emergency roadside assistance, I'm not aware of an on-the-spot, 24-hour data center service for emergency storage capacity replenishment. Granted, some storage vendors and product providers have creative pre-positioning and marketing programs where you can access storage on-demand; however, what happens when those are exhausted?
One of the first things you need to do is identify if you are completely out of storage capacity, or if you have reached a quota for your particular storage allocation. You may not be completely out of storage capacity; you may be running on reserve capacity. It is important for you to understand how your system's performance and stability are impacted when using reserve capacity. (Warning: If you ignore the indicators and use up your reserve capacity, you may be stranded. Last I checked, AAA did not have spare gigabytes and terabytes for emergency assistance.)
In the short term, investigate whether reconfiguring your storage allocation will help. If you can, remove previously backed up and unused files. Reconfiguring and removing files may be disruptive and you have to identify what files can be removed. Also look to see what databases can be pruned, purged and compressed to free up space or if any temporary and maintenance space can be freed up. Look to see if you can you borrow storage capacity from other systems or applications or from your storage vendor. Some vendors offer storage-on-demand programs where storage is physically pre-configured onsite and you are charged when you use it.
Do you know how long the storage capacity shortage is expected to last and is it expected to get worse? If there is no more physical storage capacity onsite, how quickly can a vendor ship and install new storage to you? Keep in mind that once the storage is on your premise, the storage needs to be setup, configured and allocated to applications, all of which take time and can include possible disruptions.
Do you know how quickly you can obtain (purchase, rent or lease) more storage capacity and do you have a budget that will allow you to acquire storage? Will your environment support the addition of more storage, and do you have capacity in your existing storage systems to add disk drives, available switch ports or adapter ports to attach storage and what will the cost to upgrade applicable software license be?
If you do not have performance monitoring and resource usage tools (also known as SRM), you'll need to get some, as you will need these to be proactive and to react to future storage capacity shortages. EMC, HP, IBM, Abrevity, StoredIQ, SofTek, Tek-Tools, 3PAR and others have tools that can help identify what resources are being used. These tools can be used from a planning perspective and to react to capacity shortages, helping to identify and move data to free up capacity.
Start your spring cleaning to free up disk space and establish capacity and performance threshold alert indicators. When it comes to storage capacity threshold rules of thumbs, you will get plenty of different responses -- some based on old myths that range from keeping usage under 50% to 90% of capacity.
To avoid future capacity shortages and outages, put a storage capacity plan together. A storage capacity plan can consist of a simple outline of roughly when and how much storage you will need. If you are not sure how to put a forecast together, ask your storage vendor or product provider for help, or talk to third-party analysts and consults for advice. Check out the Computer Measurement Group (CMG) as a source of information for capacity planning. Also refer to the SearchStorage.com tip "Balance costs and demands for proper storage allocation."
Do you know…
About the author: Greg Schulz is founder and senior analyst with the IT infrastructure analyst and consulting firm StorageIO. Greg is also the author and illustrator of "Resilient Storage Networks" (Elsevier) and has contributed material to "Storage" magazine and other TechTarget venues.
06 Apr 2006
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