Flash Memory in the Enterprise

By Christine Taylor

For OpEx, you will get a significant break on energy costs. Several vendors proactively replace aging controllers and components as a competitive offering. However, carry out due diligence for high ongoing maintenance costs. Storage vendors across the board often offer a low support contract the first year, only to raise support costs the second year. Look for reasonable support costs that include 24x7 technical support with actual support engineers, as opposed to low-level script readers in a call-in center.  

All-Flash Array Vendors

AFA vendors range from established big storage vendors to hard-charging start-ups. No matter who the vendor is, subject all AFAs to a rigorous set of feature questions including high IOPs/low latency, high availability, dedupe and compression, scalability, simplicity, the ability to handle mixed workloads, reliability, native data protection and encryption, and a high degree of automation.

High IOPs / low latency

The ability to provide high bandwidth, high IOPs and low latency is fundamental to flash performance. High performance is crucial for mission-critical applications and also accelerates business-critical applications like Exchange. This data center-wide benefit goes a long way towards adding value to the AFA purchase.

IOPs and latency are related but not synonymous: input/output per second is the total number of transactions that storage is capable of processing every second. IOPs does not specify the amount of data processed per transaction, only that there was a transaction. Latency is the amount of time it takes storage to deliver a single storage transaction, such as launching reads and writes.

Decreasing latency is particularly important because of cumulative wait time. Latency lag measured in fractions of seconds might not seem to have a big impact. But multiply that single lag across thousands to millions of IO processes per month per application. The cumulative effects can badly impact application performance. AFAs with sub-millisecond latency will significantly speed up application performance.

The best AFAs will provide high performance and low latency to a variety of workloads. Here are the questions to ask vendors about your application needs:

· How sensitive are your applications to IOPs and latency? Many business applications will benefit from high IOPs/low latency. Others require it. Other applications like voice over IP, streaming, or massive online environments need high IOPs/low latency. Large virtualized environments are also prime targets for low latency.

· What does your access pattern look like? For example, VDI is write-centric while databases are read-centric. Very fast flash reads will greatly benefit read-centric databases applications with dramatically lower latency. Write-centric applications like VDI will also benefit from flash’s far superior write performance over disk.

· What is your typical block size? 4KB is the standard block size for HDD and flash storage. Some newer AFA entrants replace 4KB larger variable block sizes up to 64KB. This enables efficient and flexible block alignment with applications.


Look for an AFA that scales economically and non-disruptively. Non-disruptive features should include capacity expansion, controller upgrades, and software updates to maintain data without performance loss. Controller upgrades should be non-disruptive and not force a new array purchase. Industry-standard SSD form factors help to make AFAs highly scalable with features like stateless hot-swap controllers, separate expandable storage shelves, and hot-swap drive carriers that do not cause downtime when serviced or replaced.

Mixed workloads

Modern data centers have a variety of workload types generated from hypervisors, databases, Exchange, test/dev VDIs, and more. AFAs should provide high performance to all production data regardless of workload type. For example, a video file is sequential: no matter how large it is, IO is predictable and easier to read and write. Random access IO cannot be reliably predicted. Virtualized environments are infamous for random IO as multiple VMs stream interleaved IO to the shared storage array. Any type of storage will handle sequential relatively well; random access is where the rubber hits the road and where flash’s high performance has a distinct advantage over HDDs.

Deduplication and compression

Flash deduplication and compression allow flash arrays to offer high capacity. Ideally dedupe and compression should have a minimal effect on performance.

Inline dedupe and compression are critical to preserving capacity in fast-growing data environments. Here is why inline matters: reducing data as it is coming into the array greatly reduces capacity requirements. Dedupe ratios will vary depending on the application but should deliver a minimum of 4:1. Dedupe-friendly applications like databases could see upwards of 10:1.

With flash, dedupe not only preserves capacity but also improves the performance of an all-flash array. Data dispersion helps flash take advantage of higher parallelism, and reduces the writes that eventually wear down SSDs.


Simplified installation, training, and management relieve IT of heavy storage burdens. This is particularly important to smaller data centers that operate with a small staff of IT generalists.  These data centers experience the same growth rates as the larger environments, and must manage without adding more staff. Simplicity is the best means to meet this goal without sacrificing quality.

For example, the AFA should offer highly configurable settings using a wizard and automated processes. Simplified management will include operations like growing and shrinking volumes, monitoring capacity and performance, managing hosts and host groups, and managing snapshots.  Add automatic remediation for errors to dramatically shift the management burden from administrators to the storage system.

Reliability and protection

Reliability and availability depend on AFA architecture and native data protection services. For example, active/active IO handling protects against application outages; crucial to mission-critical applications. In this configuration, connectors between dual controllers transfer IO traffic from a failed controller or component to the other controller. Flash arrays that store all data writes in persistent NVRAM before writing to SSD will also ensure data consistency. RAID optimized for flash is also crucial to reliability. Far from being an outdated HDD protection feature, flash RAID actually improves performance in flash environments with much faster rebuilds thanks to uniform distribution of parity bits across multiple drives. And with flash, it is possible for a RAID design to rebuild data in a many-to-many configuration.

Data protection/DR is also vital for AFAs. Older Tier 0 flash products did not offer data protection services in the data path but things have changed for Tier 1 flash storage. New AFAs should offer native snapshots and data replication functionality. Performance impacts from snapshots are not an issue with flash, which accelerates data protection operations above HDD or hybrid-based DP. Capacity can be an issue on flash; be sure that your AFA is space efficient by deduping and compressing snapshots.

Photo courtesy of Shutterstock.

This article was originally published on November 18, 2015

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