3 min read

Breaking the Barriers of Physical Hardware with System Managed Mirroring

Virtualization is the DNA of DataCore. A pioneer of software-defined storage (SDS), DataCore started breaking through physical barriers that kept storage isolated in silos as early as 1998.  The very first step was converting any raw physical disk on a Windows server into a virtual disk, and serving it over an Arbitrated Loop Fiber Channel network to numerous Windows servers.  In the years that followed, raw disks were aggregated in thin-provisioned pools, and virtual disks of varying sizes served to an expanding list of servers such as Windows, Unix and Linux.

Utilizing two DataCore SANsymphony servers, maintaining high availability via synchronous mirroring was yet another virtualization feat by DataCore R&D.  Leveraging commodity Host Bus Adapters (HBA), SANsymphony drivers effectively converted an HBA, originally designed to be utilized as an initiator, to either a SCSI initiator or target.  Working within the SCSI specifications, SANsymphony was capable of placing each port, in SCSI initiator and target modes simultaneously. Virtualizing FC ports, configuring them in dual roles, allowed SANsymphony to present internal mirror LUNs between two SANsymphony servers for synchronous mirroring of write I/Os.  To operate efficiently within Windows, SANsymphony was limited to configuring only 255 LUNs on each I-T Nexus.  Thus, the number of mirrored virtual disks was determined by the number of each distinct I-T Nexus.

As digital transformation expanded in every industry, and the online presence of both personal and commercial interests grew, the demand for storage grew year over year.  Twenty years ago, most sophisticated SANsymphony configurations consisted only of mirrored virtual disks numbering in the double digits. Today, in enterprises around the world, the use of mirrored virtual disks is in the hundreds and thousands.

Enterprise-class configurations require HBAs with multiple ports to overcome the 255 mirrored virtual disk limit per each I-T Nexus, thus pushing against the physical limits of servers. Increasing the number of HBAs, requires additional server slots to accommodate more HBAs and Ports. Once again limitations and barriers enforced by physical hardware required a solution based on virtualization.

DataCore’s system managed mirroring (SMM), broke barriers enforced by physical hardware. Instead of confinement by hardware limitations, our world-class engineers worked magic inside those very same LUNs. With just one LUN, SMM can service mirror I/O for up to 2000 virtual disks; one I-T Nexus can support 255 LUNs.

Let us consider a configuration with just two mirror ports per SANsymphony server with direct connections; essentially this provides two distinct I-T Nexus.  Without SMM, the upper limit of mirrored virtual disks is 510. The same exact configuration with SMM can support 510 multiplied by 2000 virtual disks…you do the math.

Due in part to innovation in the virtualization of hardware resources like SMM, as well as a continued legacy of breakthroughs in software-defined storage, it should come as no surprise that DataCore remains and maintains its leading role in the storage industry.

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