ESXi 5.5 was the answer. While the version number suggests a "point release," the features introduced were major architectural leaps. The build number specifically refers to the initial General Availability (GA) release of the ESXi 5.5 hypervisor, the 64-bit (x86_64) architecture that became the standard for enterprise servers. Key Features of ESXi 5.5.0 Build 1331820 The release of this ISO brought several features that are now considered standard but were revolutionary at the time. 1. VSAN (Virtual SAN) Readiness Perhaps the most significant feature introduced alongside ESXi 5.5 was the unveiling of VMware Virtual SAN (VSAN) . While VSAN was in "beta" or "public beta" during the initial 5.5 release phase, the hypervisor architecture included the foundational code required to aggregate local storage of ESXi hosts into a shared storage pool.
This article explores the significance of the ESXi 5.5.0-1331820 release, its groundbreaking features, the hardware it supported, and the context of its 2013 debut. To understand why VMware vSphere Hypervisor ESXi 5.5.0-1331820 was so significant, one must look at the state of the industry in 2013. ESXi 5
This change was crucial for database administrators and companies running large file servers. It allowed monolithic applications to be virtualized without complex workarounds involving spanning disks or raw device mappings (RDMs). Build 1331820 introduced vSphere Flash Read Cache (vFRC) . This feature allowed administrators to leverage solid-state drives (SSDs) as a dedicated cache layer for virtual machines. Key Features of ESXi 5
Before this, virtualization relied heavily on expensive SAN (Storage Area Network) arrays. The ESXi 5.5 ISO marked the beginning of hyper-converged infrastructure (HCI), allowing companies to use local server disks for shared storage, drastically lowering the barrier to entry for high-availability clusters. In the era of "Big Data," the previous file size limits for virtual disks were becoming a bottleneck. Prior to 5.5, the maximum size for a Virtual Machine Disk (VMDK) was 2 TB. With the ESXi 5.5.0-1331820 release, VMware increased this limit to a staggering 62 TB . While VSAN was in "beta" or "public beta"
The build number, , was crucial for verifying integrity. System administrators would often check the build number in the console to ensure they were deploying the GA release rather than a patched update. Following the release of 1331820, VMware
In 2013, SSDs were expensive but incredibly fast. vFRC allowed IT teams to use a smaller amount of expensive SSD storage to accelerate the performance of VMDKs sitting on slower, cheaper spinning hard drives (HDDs). This was a critical performance optimization technology before all-flash arrays became affordable. The x86_64 ISO format of this release signaled the final nail in the coffin for 32-bit server virtualization. ESXi 5.5 dropped support for several older processors, focusing entirely on the 64-bit x86 architecture. This optimization allowed the hypervisor to support significantly higher amounts of physical RAM (up to 4 TB per host) and more logical processors, paving the way for the high-density server consolidation strategies used today. The "Free Hypervisor" vs. The Commercial Stack The keyword for this article specifically references "VMware vSphere Hypervisor," which is the free edition of ESXi. In 2013, the ESXi 5.5.0-1331820 ISO was available for free download with a license that never expired.
The ISO contained the necessary bootloader and the hypervisor kernel (VMkernel). Upon booting from the ISO via a CD-ROM or mounted virtual media, the installer guided the user through a text-based interface. The hardware detection was robust, automatically identifying network interface cards (NICs) and storage controllers.
