1. VMware ESXi Server Down
If your ESXi host is down/unreachable:
Basic Checks
Ping the host IP.
Try connecting via vSphere Client / vCenter.
Check if management network (vmk0) is up.
Console Access
Log in to the DCUI (Direct Console User Interface) on the server.
Check if Management Network is disconnected.
Restart Management Agents from DCUI.
Hardware Issues
Verify server power (PSU, cables).
Check iLO/iDRAC/IMM for hardware alerts.
Look for memory/disk/CPU failures.
Network Issues
Check NIC connectivity (link lights, switches).
Verify VLAN & IP config.
Storage Issues
If datastore inaccessible → check SAN/iSCSI/FC connectivity.
Verify LUN presentation from storage team.
Logs & Recovery
Check /var/log/vmkernel.log & /var/log/hostd.log.
If corrupted, reboot host (after maintenance window).
If ESXi fails to boot → check boot device (SD card/SSD).
🔹 Step-by-Step Explanation of Ballooning, Compression & Swapping in VMware ⸻ 1️⃣ Memory Ballooning (vmmemctl) Ballooning is the first memory reclamation technique used when ESXi detects memory pressure. ➤ Step-by-Step: How Ballooning Works 1. VMware Tools installs the balloon driver (vmmemctl) inside the guest OS. 2. ESXi detects low free memory on the host. 3. ESXi inflates the balloon in selected VMs. 4. Balloon driver occupies guest memory, making the OS think RAM is full. 5. Guest OS frees idle / unused pages (because it believes memory is needed). 6. ESXi reclaims those freed pages and makes them available to other VMs. Why Ballooning Happens? • Host free memory is very low. • ESXi wants the VM to release unused pages before resorting to swapping. Example • Host memory: 64 GB • VMs used: 62 GB • Free: 2 GB → ESXi triggers ballooning • VM1 (8 GB RAM): Balloon inflates to 2 GB → OS frees 2 GB → ESXi re...
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