Unified data storage: Benefits and challenges

Unified data storage, or multiprotocol storage, provides storage managers with block- and file-based access in one device. However, this doesn't mean it can present the same data at the block and file level.

Unified data storage provides enterprise data storage managers with block- and file-based access in one device. This cuts energy costs as well as the complexity and administration time required to keep a separate SAN and NAS subsystem. In this interview, SearchStorage.co.uk Bureau Chief Antony Adshead speaks with Chris Kranz, senior technical consultant at B2net, about the definition of unified data storage, benefits and challenges of the technology, as well as some use cases and limitations.

You can listen to the interview as an MP3 or read the transcript that follows.

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SearchStorage.co.UK: What is unified data storage or multiprotocol storage?

Kranz: It's a unified means of addressing storage using a variety of access protocols. Some of the more common methods of block-based storage include SAS, Fibre Channel [FC], iSCSI and now Fibre Channel over Ethernet [FCoE]. File-based access tends to just be NFS and CIFS, but can include other transport methods such as FTP and HTTP.

There are a large number of products today that allow multiprotocol access. These vary from large storage systems addressing many petabytes down to the other end of the scale -- simple servers that present local disk with many interfaces.

Multiprotocol means different things to different vendors, but the basic capability will include the ability to present block- and file-level storage in the same product. However, despite a single appliance being able to present multiple protocols, this doesn't mean it can present the same data at block level and file level.

Block-level access gives the system receiving the storage the perception of direct access to the underlying disk. Often, this is done through a virtual layer where the storage appliance can still have some control of the data in the layout.

The server still needs to place its own file system on top of this block-level storage, so the use cases are as varied as the products available. File-level access allows multiple end users or systems to access the same data. The file system is controlled by the storage appliance, so there is much more control over the data in the layout.

Often deduplication, compression, security and encryption are used in conjunction with file-level access as the storage system can have direct control over the data and files.

Some vendors address unified storage by putting together a variety of systems that make up a single storage pool. This often has a front-end gateway appliance or server that does the conversion from a SAN's native protocol into multiple protocols to suit different applications. This allows virtualisation of the storage and complete transparency from where the storage is actually allocated. This also allows separation from a dependency on a particular storage vendor. However, it does leave a dependency on a gateway vendor.

Other vendors supply multiprotocol storage solutions, but in a limited fashion, so you may be able to choose from a SAN-based iSCSI and Fibre Channel solution, or a NAS-based NFS and CIFS solution, but not both. This limitation is seeing a decline, however, as vendors are making use of gateway appliances or multiprotocol functionality directly in the storage system.

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