SAN (Storage Area Network) Failure
A SAN failure rarely means a single thing went wrong. It usually means a failure occurred somewhere in a stack of several layers — physical disks, a RAID or erasure-coding layer, LUN presentation, and often a file system or database on top of that — and recovery starts with figuring out which layer actually broke.
What's actually happening
A Storage Area Network presents "LUNs" (logical units) to servers as if they were plain disks, but underneath, a SAN controller manages pooled physical drives through its own RAID or erasure-coding scheme, its own caching and metadata layer, and often deduplication or thin-provisioning logic specific to that vendor. A failure can originate at any layer — a controller malfunction, a firmware bug during an update, multiple physical disk failures exceeding what the underlying redundancy tolerates, or corruption introduced by the SAN's own management software — and each layer requires different expertise to diagnose and reverse.
How recoverable this really is
Depends entirely on which layer failed, and how far that's already been compounded by follow-up troubleshooting. A controller or metadata-layer problem with the physical disks intact is often very recoverable; extensive physical disk loss beyond the array's redundancy is a fundamentally harder problem, similar in kind to the harder end of RAID array failure but at a larger scale, with vendor-specific complexity layered on top.
The general approach
This almost always starts with working directly with the SAN vendor or a lab experienced with that specific platform, since proprietary controller logic, metadata formats, and sometimes the vendor's own diagnostic tools are usually necessary just to understand the failure state accurately before any reconstruction can begin.
Don't let a SAN controller auto-heal, reinitialize, or apply a pending firmware update while it's already in a degraded or faulted state. Enterprise storage systems often queue exactly these kinds of automated actions, and letting one run on a system that's already partially failed is one of the more common ways a contained SAN incident becomes a full outage.
Practical, step-by-step guides for specific recovery software will be added here as separate linked articles.
This page describes the general situation, not a guaranteed fix for your specific case. If you'd rather have someone experienced take a look before you try anything, see what a hands-on evaluation looks like.