Introduction

As one reflects on the state of storage over the past couple of decades, two primary metrics come to mind by which storage has traditionally been measured. First, there is the “dollars per GB” or “dollars per TB” metric, which expresses how much storage can be had for a particular dollar amount. Second, there is the “dollars per IOP” metric, which tells CIOs how much performance can be purchased as part of that storage.

Although the capacity metric has trended steadily downward over time for traditional rotational storage, the performance metric has remained relatively high. In order to meet application performance needs, organizations needed to purchase additional storage, even if that meant buying additional capacity that wasn’t necessarily needed.

Today, several companies in the market are trying to solve this performance dilemma through the creative application of flash-based storage. However, moving to an all-flash storage system simply flips the problem; organizations may end up with the performance they need but far too little capacity, or capacity at too high a cost.

The vendor I’ll be discussing in this article is taking a balanced, cost-conscious approach in an attempt to bring the two metrics — capacity and performance — into closer alignment to allow organizations to meet their needs without breaking the bank.

About Nimble Storage

Nimble Storage was founded in 2008 and started shipping product in 2010. Today, with 450 customers and close to 1,000 devices shipped, Nimble has set its sights on the midmarket space — 200 to 2,000 employees — with storage needs in the 50 TB range. These customers are typically heavily virtualized, but they do not have an army of IT staff. As such, these organizations are looking for homogenous, easily-managed, cost-effective storage.

About the solution

Nimble brings a combination of high performance flash and low cost SATA storage to a purpose-built iSCSI-based hybrid array. Hybrid storage is an increasingly popular way for vendors to deliver solutions that capture the raw performance capabilities of flash storage while retaining the massive storage capacities that can be had with traditional rotational storage.

Based on what Nimble calls its Cache Accelerated Sequential Layout (CASL) architecture, which I will describe later, the solution fits a wide swath of application needs, including most mainstream applications such as Exchange, VDI, SharePoint, and web/file/print. Nimble admits that the company’s solutions are not for everyone. For those with intensive real-time analytics needs, a pure flash solution is often better, and for those with significant long-term archival needs (“cheap and deep” storage needs), a more capacity-focused solution is often a better option. That said, an organization could still acquire Nimble for its mainstream needs and consider other solutions for the two outlying use cases described.

In the Nimble solution, the flash storage is as nothing more than a cache, which is used to accelerate read operations while the SATA disks are used for storage. Because the flash is simply cache and is not an actual data tier, the Nimble solution is tierless. Administrators do not need to concern themselves where data is stored.

Because Nimble’s array is highly efficient with regard to the way that it handles array-based snapshots, customers can also expect to be able to cost-effectively retain up to 90 days of backups on the array. Obviously, this is not disaster recovery protection, but does support very quickly recovery from an administrator error or system failure. For disaster recovery, Nimble supports replication to another device in a DR site.

There’s no need to move data to or from tape or other backup media, so backups and restores can be performed in seconds.

CASL

Nimble’s CASL architecture is built from the ground up to support the company’s hybrid array. This is not a legacy architecture layered on top of flash. CASL provides a number of features:

• Universal compression: This is part of Nimble’s value proposition. Whereas some architectures use fixed-size blocks, CASL uses variable-size blocks, enabling better levels of compression. Nimble claims 2-4x data compression through this technique. Often the guidance is to disable these kinds of compression techniques due to performance. Variable block size improves compression opportunities and increased reduction.
• Write-optimized layout: Through Nimble’s write optimizations, the company claims 100x improvement in write performance. Writes are buffered in NVRAM to aid in improving performance. Random writes are always organized into large sequential stripes. When coupled with the use of low-cost, high-density HDDs, compression substantially lowers costs.
• Smart caching: Improves reads by 50x with metadata always stored in flash and quickly accessible. Nimble also converts random writes to sequential writes to minimize write amplification, which allows the use of less expensive MLC SSDs.

Cost and differentiation

The Nimble storage solution carries with it costs that are reasonable for both capacity and performance. Nimble estimates the capacity cost of their solution at $1 to $1.50 per GB. On the performance side, $1 to $2 per IOPS.

Again, by using less expensive MLC flash and 7.2K RPM SATA disks, Nimble is able to keep costs reasonable while still meeting performance needs.

Support

The Nimble array regularly phones home to report to HQ the current status of, well, pretty much everything from hardware errors to MPIO configuration issues that could be affecting performance. Support proactively contacts customers or corrects issues in order to ensure a good customer experience. Through anonymized aggregated telemetry, Nimble can also help customers learn from one another.

Customers are certainly using the features found in the product. Nimble estimates that the percentage of customers taking hourly snapshots is north of 73%.

Action Item: CIOs considering a storage move that don’t have needs that sit outside Nimble’s core competencies should consider the company’s solution to see if it can meet capacity and performance goals. As a midmarket play, Nimble is worth a look from those with small IT staffs that need to keep things simple and affordable.

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