Author: Danilo Chiacchio

Linux swap usage can sometimes look confusing, especially when a server still has several gigabytes of available memory. At first glance, this may seem like a sign of memory pressure or poor system performance. In reality, Linux memory management is designed to use RAM efficiently rather than keep swap permanently at zero. The kernel may move inactive pages to swap even when physical memory is still available. Understanding Linux swap usage requires looking beyond the amount of free memory. Swap activity, available RAM, page faults, workload behavior, and kernel settings provide a much clearer picture of what is actually happening.…

Lustre is a parallel file system designed for workloads that need shared access to large datasets and high aggregate throughput. It is widely used in high-performance computing (HPC), where many clients may access data across multiple storage targets. Unlike a conventional local file system, Lustre separates file metadata from file data. Metadata services manage names, directories, permissions, and file layouts. Storage services provide the file contents, and clients can access data directly from the servers hosting the relevant targets. This separation enables parallel I/O, but performance depends on the workload, network, client configuration, and storage hardware. This article explains the…

Recover ESXi Host Network shows all the necessary steps to recover an ESXi management network when connected to a vSphere Distributed Switch (VDS). First things first: Describing the Scenario So, in this example, we have a four-node vSAN cluster, and the first ESXi host, for some reason (wrong configuration such as VLAN tagging, etc), is with “not responding” status, as we can see: All nodes are using a vSphere Distributed Switch (VDS), and all VMkernels adapters communicate through Port Groups attached to this VDS: Each ESXi host has four physical adapters: Each Port group uses two physical adapters: one Active…

tmux on Linux is one of the tools I rely on most when working on remote servers and managing multiple terminal tasks simultaneously. Instead of opening several terminal windows, I use tmux to organize sessions, split the screen into panes, and keep long-running processes active even after disconnecting from an SSH session. In day-to-day Linux administration, tmux makes it much easier to monitor logs, edit configuration files, execute maintenance tasks, and work with multiple remote systems from a single terminal window. Its lightweight design and wide availability across Linux distributions make it an essential utility for system administrators and developers…

A Slurm node DRAINED state means the scheduler has intentionally prevented a compute node from receiving new jobs. This usually happens because Slurm, a health-check mechanism, or a cluster administrator identified a condition that makes the node unsuitable for additional workloads. Seeing drain or drained in sinfo does not immediately tell you what failed. The node may have a hardware problem, a full filesystem, an invalid Slurm configuration, a failed Prolog or Epilog, or simply have been drained manually for maintenance. Fortunately, Slurm normally stores a reason with the node state. By combining sinfo, scontrol, system logs, and a few Linux checks, an administrator can usually determine exactly why the…

Recovering an NSX Manager cluster from a file-based backup requires more than deploying a replacement appliance. The restore point, NSX version and build, appliance identity, repository access, and backup passphrase all need to meet the requirements for that recovery. A mismatch can leave the Restore action unavailable or prevent the restore from completing. This lab walkthrough covers recovery after all three NSX Manager appliances became unavailable while the Edge Transport Node VMs remained in the vSphere environment. It follows the restore workflow from deploying the first Manager through rebuilding the cluster, reconciling the surviving Edge nodes, and validating the recovered…