FAQ

Examining new features in storage-area network (SAN) technology

Like other storage technology markets, the storage-area network (SAN) landscape is evolving as vendors and users focus on cost reductions and efficiency improvements. In this SearchStorage.co.UK podcast, Ian Lock of GlassHouse Technologies UK discusses the latest developments in the SAN market. Click on the podcast or read the transcript below to get Lock's take on key developments in SAN technology, opportunities for cutting energy costs and increasing disk utilisation with SANs.

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>>What is driving the latest developments in SAN products?
>>Which SAN features are helping make better use of disk space?
>>Which SAN features are aimed at cutting energy costs?
>>What other key trends are we seeing in SAN products?

What is driving the latest developments in SAN products?

The drivers for the latest developments in SAN products reflect the ongoing focus on cost reduction and efficiency improvements. Many IT managers have been asked to do more with less as they have seen their budgets frozen or cut.

The first driver is to make better use of disk space. This could mean reducing the amount of storage capacity consumed, for example, by use of data deduplication. It could also mean improving disk space utilisation through storage management or reporting tools, or it could mean preventing over-provisioning or over-reservation by improving storage processes.

The second driver is to make better use of energy and data centre space. Larger disk sizes have led to better rates of storage density which allows for more efficient use of the data centre floor space. Most data centre managers are facing constraints on the power and cooling capacity of their data rooms, so systems which consume less energy and generate less heat are of increasing interest.

The third driver is the use of SANs by smaller organisations. The benefits of shared storage, including centralised control and the flexibility to share capacity between multiple hosts, have continued to filter down to smaller organisations. Therefore, vendors continue to focus on products which are cost effective and easy to use by smaller companies.

What SAN features are helping make better use of disk space?

Three SAN features improving the use of disk space include data deduplication, thin provisioning and dynamic tiering. Data deduplication eliminates duplicated files or blocks of data from storage volumes. The devices work in one of two ways; inline or post-process.

Inline systems sit in the data path between host and target, removing duplicated blocks of data before they are written to disk. Post-process systems search through data after it has been written to disk, identifying repeated data before creating a new, deduplicated version. Dedupe has the potential – depending on data type - to reduce the size of disk volumes, anywhere from 50% to 95%.

So far, dedupe has mainly been a feature of disk backup and virtual tape library (VTL) products. But the crossover of dedupe to online volumes has already started with some vendors building the feature into their network-attached storage (NAS) systems.

Another feature which can boost utilisation levels is thin provisioning. Thin provisioning allows a storage array to present more capacity to attached hosts than it physically has installed. Raw capacity is added only as it is consumed by attached host servers. With thin provisioning, storage utilisation can be improved with a reduced capital cost. However, the storage team must keep a close watch on the management interface to ensure the disk pools are kept topped up.

By moving data between tiers of storage on the fly without causing host or application outages, dynamic tiering is another SAN feature that can boost utilisation levels.

What SAN features are aimed at cutting energy costs? 

Spin-down technology, synonymous with massive array of idle disks (MAID) technology, refers to the spinning down of individual or groups of disk drives when they're not being accessed. This results in cost savings for power and cooling since most power used by an array is to keep drives constantly spinning. Taking spin-down to its logical conclusion you end up with disk drives that don't spin at all – solid state drives (SSD). SSD is a collection of high grade flash memory chips and a controller which is packaged to emulate a disk drive. This is a rapidly developing section of the market, with the latest SSDs showing performance improvements over mechanical drives and lower power demands. However, costs are still high so the sweet spot for SSD will be at the high performance end of the market.

Some of the technologies already mentioned have an indirect effect on energy costs as well. Storage re-tiering – if data migrates from mirrored, replicated and cloned storage onto RAID 5 non-replicated storage and then allows you to decommission those tier 1 RAID frames - will reduce the total number of drives needed per gigabyte and boost power and cooling cost savings.

Thin provisioning should also reduce power and cooling costs as the number of drives purchased and kept running is reduced.

What other key trends are we seeing in SAN products?

Other trends include the widespread take up of iSCSI and multi-protocol storage. The realisation that many servers never use more than a fraction of the storage bandwidth which Fibre Channel (FC) provides is driving the take up of iSCSI. Also the acquisition of iSCSI vendors by larger, broad-based vendors has helped make iSCSI more accessible to a wider storage consumer base and given it widespread credibility.

Multiprotocol storage is the provision of access to a storage platform via a wide choice of protocols, including CIFS, NFS, iSCSI or FC. Therefore storage can be presented to multiple host servers in the format they require. Applications requiring file sharing and file-level access can connect to storage via CIFS and NFS while applications requiring block-level access can connect via iSCSI or FC.

Multiprotocol storage consolidates separate legacy SAN and NAS arrays into a smaller number of combined multiprotocol arrays which simplifies administration and lowers support costs.


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This was first published in November 2009

 

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