Flash storage would seem to be the answer to application performance problems. By replacing spinning hard disks with solid-state flash drives, organizations can reduce storage latency to one or two milliseconds or less. That makes flash ideal for data analytics, high-transaction databases and other storage-intensive applications.
Thing is, flash storage doesn’t exist in a vacuum. Often, when organizations implement flash, weaknesses in other aspects of the IT environment become all too apparent. If flash doesn’t deliver the expected performance gains, your storage-area network (SAN) may be the culprit.
The SAN: A Primer
The SAN is a separate high-speed network dedicated to storage, allowing multiple servers throughout the data center to access shared storage devices as if they were directly attached. This any-to-any connectivity is known as the storage fabric. The devices are interconnected using switches and communicate via specific protocols.
One such protocol is Fibre Channel, which is the underlying technology in many large enterprise SANs. Fibre Channel switches are known for their ability to deliver high levels of performance and availability with low latency and lossless data transmission. They’re also notorious for their cost, complexity and management headaches.
That’s why many organizations have implemented SANs using the iSCSI protocol, which allows storage devices to communicate over Ethernet networks. IT teams understand Ethernet very well, and would rather set up a SAN using familiar technology than have to dedicate resources to managing Fibre Channel. However, iSCSI is much slower than Fibre Channel and puts a greater burden on a server’s CPU. In addition, iSCSI is often implemented incorrectly, amplifying performance problems.
Time for an Upgrade?
Many iSCSI SANs were built using 1GbE switches, which will likely need to be upgraded to 10GbE or even 25GbE to obtain the bandwidth needed to support flash. Fibre Channel SANs based upon 16Gbps switches will also need to be upgraded to the latest 32Gbps technology.
Some organizations may consider replacing their iSCSI SANs with Fibre Channel. Another option is Fibre Channel over Ethernet, which makes it possible to run Fibre Channel traffic on Ethernet infrastructure.
Note, however, that both Fibre Channel and iSCSI rely on the SCSI protocol for communication between applications and storage devices. SCSI adds a good deal of latency, particularly with I/O-intensive workloads. That may have been OK with traditional hard disks, but won’t allow you to obtain maximum performance from your flash storage devices.
The Future of Flash Connectivity
Non-Volatile Memory Express (NVMe) helps to relieve those bottlenecks. NVMe is a storage interface designed specifically for flash, with a more streamlined protocol that reduces latency and improves performance.
Last year, NVM Express, Inc., released the NVM over Fabrics specification for accessing storage devices and systems over Ethernet, Fibre Channel and other storage fabrics. One option uses remote direct memory access (RDMA) to transfer data without involving a server’s processor; it can be implemented over Ethernet using adaptor cards. The other option uses Fibre Channel to support NVMe, and can be implemented by upgrading the software on existing switches.
Flash storage can deliver significant performance gains but can also expose other weaknesses in your storage environment. Let Sequel help you rearchitect your SAN to get the most from your flash storage investments.