Published on Sunday, 18 March 2012
Avere Systems, NAS optimisation specialist, designs NAS specifically to scale performance
and capacity separately, accessing Flash-based storage media using real-time tiering.
|When companies running NAS Network-attached storage need to increase performance of their systems, typical upgrades include adding more hard disk drives or short-stroking HDDs, that is, deliberately restricting a HDD in order to reduce seek time and increase the available in and out ops, or IOPS, from the drive. Other common measures are installing Flash PCI cards or solid state drives, or upgrading to higher performance, more expensive NAS controllers.
According to Avere Systems some methods can increase costs and may be short-term solutions that aren’t able to scale up with growth and diversity in an organisation. Avere has identified some considerations to be aware of when planning NAS upgrades.
The total cost of adding HDDs to an existing or planned NAS infrastructure extends beyond the cost of hard disk media. As well as enterprise-class fibre channel drives, power and cooling, rack space and data-centre floor space are other costs to factor in.
Also, because HDDs aren’t necessarily efficient at providing IOPS, adding HDDs to achieve performance goals may not be a good investment from a cost-performance point of view. Overprovisioning capacity and short-stroke drives in attempts to achieve even higher performance can also limit the overall value.
Instead of trying to extend HDD capacity, Avere says NAS users may get a better return on a storage investment by moving from a homogeneous to a tiered NAS system. Adding intelligent tiered storage able to work with newer SSDs can produce a gain in IOPS performance, and consume less power, cooling, rack space or floor space. This approach also works by recovering the capacity of existing, previously short-stroked HDDs and makes it possible for IT to use cheaper, low-speed SATA drives.
Integrating Flash storage into NAS systems is a fairly recent method used to improve performance of traditional NAS. Because cost per GB for Flash in a NAS system is much more expensive than for SATA storage, efficiency is an important consideration.
|Flash is typically added to a NAS system in one of three ways - as a PCI card, an SSD array or a caching appliance. Avere feels that PCl cards are often inefficient because they tend to be read-only, still needing extra hard drives to handle the write workload, and may also result in over-provisioning to be able to handle peak loads. The company finds SSD arrays are also inefficient because data movement to Flash is slow, not granular, and triggered by a policy engine that measures data activity across long periods and may not respond immediately to a hot application.
Avere supplies Flash in its FXT 2700 appliance, which sits in front of NAS systems from other vendors. The Avere has 512GB of Flash per appliance, scales to 25 appliances or 13TB per cluster, and accelerates both read and write workloads. The Avere architecture has a consolidated Flash layer that is shared by all of the backend NAS systems, allowing a specified amount of Flash to be added to the NAS infrastructure to deliver the required aggregate performance. The FXT 2700 moves data in real time at the granularity level of blocks within files.
Controller upgrades are a usual part of the traditional NAS lifecycle. Controllers are generally purchased to meet current performance requirements, but future performance requirements may not be factored in, due to cost. If later on, the controllers do not keep up with increased requirements, further upgrades may be needed for more performance for the data.
Avere has encountered some problems with upgrades including expense and disruption, and the need for more disks, power and space. Instead, they suggest dividing the NAS architecture into two stages by adding a performance-oriented automated tiering layer in front of the existing controllers. As more clients and new applications are added, an Avere FXT cluster can be expanded with the non-disruptive addition of new nodes. Up to 25 FXT nodes can be added to a cluster, delivering power without having to touch devices already in place. Because the Avere FXT cluster can serve multiple storage servers, Flash should not have to be added to each controller. The Avere cluster becomes an extensible fast media layer in front of all of them, providing performance to hot spots without overprovisioning.
Because a certain level of management is needed to upgrade existing NAS infrastructure, the cost of expertise could be another factor. Installing fast-access storage media solves part of the problem, but the customer needs to identify which applications are best served by the new tier of storage, and understand the storage media read and write rates and in order to optimize its utilization.
In contrast, an Avere FXT cluster includes enough intelligence to dynamically allocate data to the appropriate storage tier and media, based on data and access characteristics. This tiered NAS approach is intended to accelerate read, write and metadata operations without having to add more disks to the system. FXT appliances scale from 1 to 25 nodes per cluster, and for capacity, cheaper SATA drives can be added. Installation does not require changes to existing applications, clients, NAS systems or data retention procedure such as backup and mirroring. www.averesystems.com www.stormfx.com.au