Regardless of interconnect and platform efficiencies, deltas begin to accrue after data travels about 16 kilometers, thanks to speed-of-light constraints on signal velocity. In a communications system, propagation delay refers to the time lag between the departure of a signal from the source and the arrival of the signal at the destination. When two arrays configured in a synchronous mirror are placed 16 kilometers or more apart, the propagation delay that accrues to storage I/O signals introduces noticeable latency into application performance. Basically, the application must wait until a response is received confirming that data has been written to both the primary (local) and secondary (remote) array before it continues with the next I/O. If the arrays are configured in an asynchronous mirror, the application doesn't wait for the confirmation of a write at the remote location. However, deltas reflect the transit time between local and remote arrays, and worsen as the two arrays are placed farther apart. Attempts to work around distance-induced latency have led to a proliferation of journaling, spoofing and caching strategies that do not so much surmount the issue of propagation delay as provide ways to live with it (see "Signal Velocity," below).
Other factors affecting the copy process may include the need to quiesce (turn off or idle) servers or applications while data copies are being made, or the requirement to do the copying within narrow windows to avoid overburdening production servers or networks with background copy tasks. In the face of many companies' 24x7x365 operating schedules, opportunities for off-line copying or backup are in increasingly short supply. Moreover, as the quantity of data that needs to be copied grows (estimates range between 40 percent and 100 percent per year, depending on the analyst), the idea of copying massive amounts of data in short windows of opportunity is becoming increasingly laughable.
Finally, pragmatic constraints, typically related to option costs, limit the data-protection alternatives in most companies. Until recently, the industry provided only two choices for copying data: disk to tape (streaming backup) and disk to disk (mirroring). Tape has been the workhorse for data protection in most companies for the past 20 years, while array-to-array mirroring over distance has provided a pricey option for those with deep pockets and zero tolerance for downtime.
Proprietary mirroring schemes have always been a cost accelerator in disk-to-disk copying. With conventional mirroring, a company must buy two arrays (three for multihop mirroring) from the same vendor to use the vendor's remote mirroring software. Today, many systems tout "vendor-neutral" software-based mirroring but require that storage arrays first be aggregated into a Fibre Channel fabric--aka a SAN--which must then be overlaid with virtualization technology to facilitate copying. Such configurations still carry hefty price tags, and that's before factoring in the ongoing cost of a WAN interconnect or the additional expense of security and encryption for remote data copies.
What you get for all this extra money, of course, is fast recovery. Disk-to-disk replication saves a lot of time and eliminates the hassle of reloading data from tape into a usable form. High-end mirroring crowd is important for certain industry segments, such as finance, whose operations are extremely sensitive to interruptions. These firms also tend to set up redundant data centers with identical gear to ensure that operations absolutely, positively will not stop.
To realize the benefits of cloud-native software, an application must actually be cloud-native—designed to run in the cloud, interacting with disaggregated cloud services, fully manageable as code—to deliver the expected benefits.
By combining resources and expertise, the AI-Enabled ICT Workforce Consortium will offer a blueprint for how industries can adapt to an AI-dominated future.
IT leaders should heed the guidance of cybersecurity insurance providers who think businesses should prioritize security education, incident preparedness, regular internal audits, and ongoing vulnerability scanning and patching.
