Simplified NFS proxy based on own NFS/XDR implementation

README.md

@@ -46,6 +46,7 @@ breaking changes in the future. However, the following is implemented:
 - Snapshot merge tool (vitastor-cli {snap-rm,flatten,merge})
 - Image management CLI (vitastor-cli {ls,create,modify})
 - Proxmox storage plugin
+- Simplified NFS proxy for file-based image access emulation (suitable for VMWare)
 
 ## Roadmap
 
@@ -53,7 +54,6 @@ breaking changes in the future. However, the following is implemented:
 - Other administrative tools
 - Plugins for OpenNebula and other cloud systems
 - iSCSI proxy
-- Simplified NFS proxy
 - Faster failover
 - Scrubbing without checksums (verification of replicas)
 - Checksums
@@ -479,9 +479,49 @@ It will output the device name, like /dev/nbd0 which you can then format and mou
 
 Again, you can use `--pool <POOL> --inode <INODE> --size <SIZE>` insteaf of `--image <IMAGE>` if you want.
 
+### NFS
+
+Vitastor has a simplified NFS 3.0 proxy for file-based image access emulation. It's not
+suitable as a full-featured file system, at least because all file/image metadata is stored
+in etcd and kept in memory all the time - thus you can't put a lot of files in it.
+
+However, NFS proxy is totally fine as a method to provide VM image access and allows to
+plug Vitastor into, for example, VMWare. It's important to note that for VMWare it's a much
+better access method than iSCSI, because with iSCSI we'd have to put all VM images into one
+Vitastor image exported as a LUN to VMWare and formatted with VMFS. VMWare doesn't use VMFS
+over NFS.
+
+NFS proxy is stateless if you use immediate_commit=all mode (for SSD with capacitors or
+HDDs with disabled cache), so you can run multiple NFS proxies and use a network load
+balancer or any failover method you want to in that case.
+
+vitastor-nfs usage:
+
+```
+vitastor-nfs [--etcd_address ADDR] [OTHER OPTIONS]
+
+--subdir <DIR>    export images prefixed <DIR>/ (default empty - export all images)
+--portmap 0       do not listen on port 111 (portmap/rpcbind, requires root)
+--bind <IP>       bind service to <IP> address (default 0.0.0.0)
+--nfspath <PATH>  set NFS export path to <PATH> (default is /)
+--port <PORT>     use port <PORT> for NFS services (default is 2049)
+--pool <POOL>     use <POOL> as default pool for new files (images)
+--foreground 1    stay in foreground, do not daemonize
+```
+
+Example start and mount commands:
+
+```
+vitastor-nfs --etcd_address 192.168.5.10:2379 --portmap 0 --port 2050 --pool testpool
+```
+
+```
+mount localhost:/ /mnt/ -o port=2050,mountport=2050,nfsvers=3,soft,nolock,tcp
+```
+
 ### Kubernetes
 
-Vitastor has a CSI plugin for Kubernetes which supports RWO volumes.
+Vitastor has a CSI plugin for Kubernetes which supports RWO (and block RWX) volumes.
 
 To deploy it, take manifests from [csi/deploy/](csi/deploy/) directory, put your
 Vitastor configuration in [csi/deploy/001-csi-config-map.yaml](001-csi-config-map.yaml),