Feature

Voice apps can strain storage

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Storage considerations
VoIP sessions can be recorded at several different compression levels and saved as different file types, but a minute of voice recording generally consumes about a megabyte of storage (see "VoIP storage requirements").

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Depending on the voice-recording system, the formats of the recordings may be proprietary or standard types, such as WAV or MP3 files. Proprietary formats typically compress better and are more secure, but they're available from only one vendor and may not be amenable to automated post-processing of the recording. A large call center might handle 10 million calls per year, with each call averaging about three to four minutes. Using four minutes as the length of an average call, and assuming that all calls are recorded, this would be approximately 40TB of data per year.

Allianz Life's experience with Witness Systems
Allianz Life Insurance Company of North America in Minneapolis reviewed various call-center products before deciding on Roswell, GA-based Witness Systems' voice-recording services. With a few exceptions, the firm was extremely happy with how well the system installed and performed. Like most organizations, Allianz Life began using DAS to retain its voice recordings. It wasn't long before the DAS arrangement became overtaxed and a storage upgrade was required.

Allianz tried tier-one storage, but found it too expensive for voice data. The company moved its VoIP data to tier-two storage, but found that it, too, wasn't a good fit for long-term storage of its voice-recording data. Allianz next turned to archive storage and felt that its EMC Centera, which hosted the firm's e-mail archives, would be a natural fit for its voice recordings.

When Allianz Life asked Witness Systems if it would consider supporting Centera's API, Witness declined, says David Kaercher, vice president of core services at Allianz. EMC said it was relatively straightforward to implement the API and estimated that the customization work to support its API would cost approximately $25,000. Allianz later learned that Witness Systems was considering introducing its own archive product and had no desire to support Centera. Nonetheless, Allianz Life still wants to move data off its tier-two storage after 30 days and now plans to archive its voice recordings on an IBM Corp. tape library. This particular Allianz Life call center receives about 100,000 calls per month, which adds up to approximately 2TB to 3TB per year. The firm plans to retain this voice data indefinitely once it's moved to tertiary storage.

Storage used for direct call recording can run the gamut from DAS to SAN or NAS boxes, and everything in between. This would be considered primary storage in call-center parlance and used as a temporary holding place for the voice recording during the highly accessed stage of its lifecycle. Once this phase has passed--usually 90 days--the voice recording could be placed on secondary storage such as lower cost disk, an archive appliance, tape or optical media. EMC Corp.'s Centera, for example, is widely used for long-term voice storage because many voice-recording systems support the Centera API.

Historically, call-center disaster recovery planning has been separate from data center disaster recovery, but this is changing because VoIP call-center recordings are increasingly being considered mission critical. "When e-mail first came out, it wasn't deemed mission critical--look where it is today," says Robyn Danz, storage specialist at CDW Government Inc. "Voice is the new e-mail."

A call center generating 10 million files annually could easily overtax a single file directory. For call-center systems generating that volume of calls, it may be prudent to place the recordings into a large database instead of dumping all of the voice files into a file directory. Retrieval of a voice record is based on the meta data associated with the call.

From a storage perspective, digital voice data looks an awful lot like the rest of your corporate data. The voice files might be larger and have more stringent real-time capture constraints, but the data needs to be online for a short period of time and then archived to a different tier of storage.

David Kaercher, vice president of core services at Allianz Life Insurance Company of North America in Minneapolis, says his company recently moved to VoIP and initially stored its voice recordings on tier-one (EMC Symmetrix) storage. As the volume of calls grew, tier-one became too expensive and the voice recordings were moved to tier-two (Network Appliance Inc. NAS) storage. Tier-two proved too expensive for long-term retention, so Kaercher wanted to move the voice data to an EMC Centera, which Allianz uses for e-mail archiving. But Kaercher couldn't convince the firm's VoIP vendor, Roswell, GA-based Witness Systems Inc., to support Centera's API. Today, Allianz is reconsidering its use of the Witness VoIP product and is planning on archiving voice recordings on an IBM Corp. tape library (see "Allianz Life's experience with Witness Systems").

This was first published in April 2006

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