In VMware ESXi the All Paths Down (APD) or Permanent Device Loss (PDL) condition is what occurs on an ESX/ESXi host when a storage device is removed in an uncontrolled manner from the host (or the device fails), and the VMkernel core storage stack does not know how long the loss of device access will last. A typical way of getting into APD would be a Fiber Channel switch failure or (in the case of an iSCSI array) a network connectivity issue. But there are also other scenarios that we will discuss later. VMware vSphere […]
There are different reason where you can you loose or corrupt your partition table of your VMFS volumes: resignature from another system (for example the backup server, if connected in SAN mode), a human mistake (datastore / delete), or maybe some storage issues. In this case usually the VMFS partition is still there and also the related data: you have “only” to rebuild the right partition table. But this could really simple if you follow the recommended practice to have only one VMFS partition on each disk. In this case you have only to build […]
With a vSphere 5 upgrade there is an important vDesign decision: if you already have some VMFS3 datastores could be better upgrade them to the new version of build new datastores directly with VMFS5? The upgrade procedure is quite fast and friendly and could be applied to a live datastore, so seems that there isn’t a big different between an upgrade or a clean format. But usually the recommendation is to re-format each LUN to VMFS-5 rather than upgrade it. This will fix a number of issues, including:
One of the “issue” with vmdk in thin format is that they start “small” and then grow when you add new data… But when you delete some data, the vmdk file size is not reduced. To be honest this issue is more related to the guest file systems that does never delete the block data, but only the metada (or some of them). Of course at guest OS level you will see the right disk usage, but this will probably not match the one that you see at VMware level (that usually will be bigger).