diff --git a/src/tape/media_pool.rs b/src/tape/media_pool.rs
new file mode 100644
index 00000000..4064d32e
--- /dev/null
+++ b/src/tape/media_pool.rs
@@ -0,0 +1,483 @@
+//! Media Pool
+//!
+//! A set of backup medias.
+//!
+//! This struct manages backup media state during backup. The main
+//! purpose ist to allocate media sets and assing new tapes to it.
+//!
+//!
+
+use std::path::Path;
+use anyhow::{bail, Error};
+use ::serde::{Deserialize, Serialize};
+
+use proxmox::tools::Uuid;
+
+use crate::{
+    api2::types::{
+        MediaStatus,
+        MediaSetPolicy,
+        RetentionPolicy,
+        MediaPoolConfig,
+    },
+    tools::systemd::time::compute_next_event,
+    tape::{
+        MediaId,
+        MediaSet,
+        MediaLocation,
+        Inventory,
+        MediaStateDatabase,
+        file_formats::{
+            DriveLabel,
+            MediaSetLabel,
+        },
+    }
+};
+
+pub struct MediaPoolLockGuard(std::fs::File);
+
+/// Media Pool
+pub struct MediaPool {
+
+    name: String,
+
+    media_set_policy: MediaSetPolicy,
+    retention: RetentionPolicy,
+
+    inventory: Inventory,
+    state_db: MediaStateDatabase,
+
+    current_media_set: MediaSet,
+}
+
+impl MediaPool {
+
+    /// Creates a new instance
+    pub fn new(
+        name: &str,
+        state_path: &Path,
+        media_set_policy: MediaSetPolicy,
+        retention: RetentionPolicy,
+     ) -> Result<Self, Error> {
+
+        let inventory = Inventory::load(state_path)?;
+
+        let current_media_set = match inventory.latest_media_set(name) {
+            Some(set_uuid) => inventory.compute_media_set_members(&set_uuid)?,
+            None => MediaSet::new(),
+        };
+
+        let state_db = MediaStateDatabase::load(state_path)?;
+
+        Ok(MediaPool {
+            name: String::from(name),
+            media_set_policy,
+            retention,
+            inventory,
+            state_db,
+            current_media_set,
+        })
+    }
+
+    /// Creates a new instance using the media pool configuration
+    pub fn with_config(
+        name: &str,
+        state_path: &Path,
+        config: &MediaPoolConfig,
+    ) -> Result<Self, Error> {
+
+        let allocation = config.allocation.clone().unwrap_or(String::from("continue")).parse()?;
+
+        let retention = config.retention.clone().unwrap_or(String::from("keep")).parse()?;
+
+        MediaPool::new(name, state_path, allocation, retention)
+    }
+
+    /// Returns the pool name
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    fn compute_media_state(&self, media_id: &MediaId) -> (MediaStatus, MediaLocation) {
+
+        let (status, location) = self.state_db.status_and_location(&media_id.label.uuid);
+
+        match status {
+            MediaStatus::Full | MediaStatus::Damaged | MediaStatus::Retired => {
+                return (status, location);
+            }
+            MediaStatus::Unknown | MediaStatus::Writable => {
+                /* possibly writable - fall through to check */
+            }
+        }
+
+        let set = match media_id.media_set_label {
+            None => return (MediaStatus::Writable, location), // not assigned to any pool
+            Some(ref set) => set,
+        };
+
+        if set.pool != self.name { // should never trigger
+            return (MediaStatus::Unknown, location); // belong to another pool
+        }
+        if set.uuid.as_ref() == [0u8;16] { // not assigned to any pool
+            return (MediaStatus::Writable, location);
+        }
+
+        if &set.uuid != self.current_media_set.uuid() {
+            return (MediaStatus::Full, location); // assume FULL
+        }
+
+        // media is member of current set
+        if self.current_media_set.is_last_media(&media_id.label.uuid) {
+            (MediaStatus::Writable, location) // last set member is writable
+        } else {
+            (MediaStatus::Full, location)
+        }
+    }
+
+    /// Returns the 'MediaId' with associated state
+    pub fn lookup_media(&self, uuid: &Uuid) -> Result<BackupMedia, Error> {
+        let media_id = match self.inventory.lookup_media(uuid) {
+            None => bail!("unable to lookup media {}", uuid),
+            Some(media_id) => media_id.clone(),
+        };
+
+        if let Some(ref set) = media_id.media_set_label {
+            if set.pool != self.name {
+                bail!("media does not belong to pool ({} != {})", set.pool, self.name);
+            }
+        }
+
+        let (status, location) = self.compute_media_state(&media_id);
+
+        Ok(BackupMedia::with_media_id(
+            media_id,
+            location,
+            status,
+        ))
+    }
+
+    /// List all media associated with this pool
+    pub fn list_media(&self) -> Vec<BackupMedia> {
+        let media_id_list = self.inventory.list_pool_media(&self.name);
+
+        media_id_list.into_iter()
+            .map(|media_id| {
+                let (status, location) = self.compute_media_state(&media_id);
+                BackupMedia::with_media_id(
+                    media_id,
+                    location,
+                    status,
+                )
+            })
+            .collect()
+    }
+
+    /// Set media status to FULL.
+    pub fn set_media_status_full(&mut self, uuid: &Uuid) -> Result<(), Error> {
+        let media = self.lookup_media(uuid)?; // check if media belongs to this pool
+        if media.status() != &MediaStatus::Full {
+            self.state_db.set_media_status_full(uuid)?;
+        }
+        Ok(())
+    }
+
+    /// Make sure the current media set is usable for writing
+    ///
+    /// If not, starts a new media set. Also creates a new
+    /// set if media_set_policy implies it.
+    pub fn start_write_session(&mut self, current_time: i64) -> Result<(), Error> {
+
+        let mut create_new_set = match self.current_set_usable() {
+            Err(err) => {
+                eprintln!("unable to use current media set - {}", err);
+                true
+            }
+            Ok(usable) => !usable,
+        };
+
+        if !create_new_set {
+
+            match &self.media_set_policy {
+                MediaSetPolicy::AlwaysCreate => {
+                    create_new_set = true;
+                }
+                MediaSetPolicy::CreateAt(event) => {
+                    if let Some(set_start_time) = self.inventory.media_set_start_time(&self.current_media_set.uuid()) {
+                        if let Ok(Some(alloc_time)) = compute_next_event(event, set_start_time as i64, false) {
+                             if current_time >= alloc_time {
+                                create_new_set = true;
+                            }
+                        }
+                    }
+                }
+                MediaSetPolicy::ContinueCurrent => { /* do nothing here */ }
+            }
+        }
+
+        if create_new_set {
+            let media_set = MediaSet::new();
+            eprintln!("starting new media set {}", media_set.uuid());
+            self.current_media_set = media_set;
+        }
+
+        Ok(())
+    }
+
+    /// List media in current media set
+    pub fn current_media_list(&self) -> Result<Vec<&Uuid>, Error> {
+        let mut list = Vec::new();
+        for opt_uuid in self.current_media_set.media_list().iter() {
+            match opt_uuid {
+                Some(ref uuid) => list.push(uuid),
+                None => bail!("current_media_list failed - media set is incomplete"),
+            }
+        }
+        Ok(list)
+    }
+
+    // tests if the media data is considered as expired at sepcified time
+    pub fn media_is_expired(&self, media: &BackupMedia, current_time: i64) -> bool {
+        if media.status() != &MediaStatus::Full {
+            return false;
+        }
+
+        let expire_time = self.inventory.media_expire_time(
+            media.id(), &self.media_set_policy, &self.retention);
+
+        current_time > expire_time
+    }
+
+    /// Allocates a writable media to the current media set
+    pub fn alloc_writable_media(&mut self, current_time: i64) -> Result<Uuid, Error> {
+
+        let last_is_writable = self.current_set_usable()?;
+
+        let pool = self.name.clone();
+
+        if last_is_writable {
+            let last_uuid = self.current_media_set.last_media_uuid().unwrap();
+            let media = self.lookup_media(last_uuid)?;
+            return Ok(media.uuid().clone());
+        }
+
+        // try to find empty media in pool, add to media set
+
+        let mut media_list = self.list_media();
+
+        let mut empty_media = Vec::new();
+        for media in media_list.iter_mut() {
+            // already part of a media set?
+            if media.media_set_label().is_some() { continue; }
+
+            // check if media is on site
+            match media.location() {
+                MediaLocation::Online(_) | MediaLocation::Offline => { /* OK */ },
+                MediaLocation::Vault(_) => continue,
+            }
+
+            // only consider writable media
+            if media.status() != &MediaStatus::Writable { continue; }
+
+            empty_media.push(media);
+        }
+
+        // sort empty_media, oldest media first
+        empty_media.sort_unstable_by_key(|media| media.label().ctime);
+
+        if let Some(media) = empty_media.first_mut() {
+            // found empty media, add to media set an use it
+            let seq_nr = self.current_media_set.media_list().len() as u64;
+
+            let set = MediaSetLabel::with_data(&pool, self.current_media_set.uuid().clone(), seq_nr, current_time);
+
+            media.set_media_set_label(set);
+
+            self.inventory.store(media.id().clone())?; // store persistently
+
+            self.current_media_set.add_media(media.uuid().clone());
+
+            return Ok(media.uuid().clone());
+        }
+
+        println!("no empty media in pool, try to reuse expired media");
+
+        let mut expired_media = Vec::new();
+
+        for media in media_list.into_iter() {
+            if let Some(set) = media.media_set_label() {
+                if &set.uuid == self.current_media_set.uuid() {
+                    continue;
+                }
+            }
+            if self.media_is_expired(&media, current_time) {
+                println!("found expired media on media '{}'", media.changer_id());
+                expired_media.push(media);
+            }
+        }
+
+        // sort, oldest media first
+        expired_media.sort_unstable_by_key(|media| {
+            match media.media_set_label() {
+                None => 0, // should not happen here
+                Some(set) => set.ctime,
+            }
+        });
+
+        match expired_media.first_mut() {
+            None => {
+                bail!("alloc writable media in pool '{}' failed: no usable media found", self.name());
+            }
+            Some(media) => {
+                println!("reuse expired media '{}'", media.changer_id());
+
+                let seq_nr = self.current_media_set.media_list().len() as u64;
+                let set = MediaSetLabel::with_data(&pool, self.current_media_set.uuid().clone(), seq_nr, current_time);
+
+                media.set_media_set_label(set);
+
+                self.inventory.store(media.id().clone())?; // store persistently
+                self.state_db.clear_media_status(media.uuid())?; // remove Full status
+
+                self.current_media_set.add_media(media.uuid().clone());
+
+                return Ok(media.uuid().clone());
+            }
+        }
+    }
+
+    /// check if the current media set is usable for writing
+    ///
+    /// This does several consistency checks, and return if
+    /// the last media in the current set is in writable state.
+    ///
+    /// This return error when the media set must not be used any
+    /// longer because of consistency errors.
+    pub fn current_set_usable(&self) -> Result<bool, Error> {
+
+        let media_count = self.current_media_set.media_list().len();
+        if media_count == 0 {
+            return Ok(false);
+        }
+
+        let set_uuid =  self.current_media_set.uuid();
+        let mut last_is_writable = false;
+
+        for (seq, opt_uuid) in self.current_media_set.media_list().iter().enumerate() {
+            let uuid = match opt_uuid {
+                None => bail!("media set is incomplete (missing media information)"),
+                Some(uuid) => uuid,
+            };
+            let media = self.lookup_media(uuid)?;
+            match media.media_set_label() {
+                Some(MediaSetLabel { seq_nr, uuid, ..}) if *seq_nr == seq as u64 && uuid == set_uuid => { /* OK */ },
+                Some(MediaSetLabel { seq_nr, uuid, ..}) if uuid == set_uuid => {
+                    bail!("media sequence error ({} != {})", *seq_nr, seq);
+                },
+                Some(MediaSetLabel { uuid, ..}) => bail!("media owner error ({} != {}", uuid, set_uuid),
+                None => bail!("media owner error (no owner)"),
+            }
+            match media.status() {
+                MediaStatus::Full => { /* OK */ },
+                MediaStatus::Writable if (seq + 1) == media_count =>  {
+                    last_is_writable = true;
+                    match media.location() {
+                        MediaLocation::Online(_) | MediaLocation::Offline => { /* OK */ },
+                        MediaLocation::Vault(vault) => {
+                            bail!("writable media offsite in vault '{}'", vault);
+                        }
+                    }
+                },
+                _ => bail!("unable to use media set - wrong media status {:?}", media.status()),
+            }
+        }
+        Ok(last_is_writable)
+    }
+
+    /// Generate a human readable name for the media set
+    pub fn generate_media_set_name(
+        &self,
+        media_set_uuid: &Uuid,
+        template: Option<String>,
+    ) -> Result<String, Error> {
+        self.inventory.generate_media_set_name(media_set_uuid, template)
+    }
+
+    /// Lock the pool
+     pub fn lock(base_path: &Path, name: &str) -> Result<MediaPoolLockGuard, Error> {
+        let mut path = base_path.to_owned();
+        path.push(format!(".{}", name));
+        path.set_extension("lck");
+
+        let timeout = std::time::Duration::new(10, 0);
+        let lock = proxmox::tools::fs::open_file_locked(&path, timeout, true)?;
+
+        Ok(MediaPoolLockGuard(lock))
+    }
+}
+
+/// Backup media
+///
+/// Combines 'MediaId' with 'MediaLocation' and 'MediaStatus'
+/// information.
+#[derive(Debug,Serialize,Deserialize,Clone)]
+pub struct BackupMedia {
+    /// Media ID
+    id: MediaId,
+    /// Media location
+    location: MediaLocation,
+    /// Media status
+    status: MediaStatus,
+}
+
+impl BackupMedia {
+
+    /// Creates a new instance
+    pub fn with_media_id(
+        id: MediaId,
+        location: MediaLocation,
+        status: MediaStatus,
+    ) -> Self {
+        Self { id, location, status }
+    }
+
+    /// Returns the media location
+    pub fn location(&self) -> &MediaLocation {
+        &self.location
+    }
+
+    /// Returns the media status
+    pub fn status(&self) -> &MediaStatus {
+        &self.status
+    }
+
+    /// Returns the media uuid
+    pub fn uuid(&self) -> &Uuid {
+        &self.id.label.uuid
+    }
+
+    /// Returns the media set label
+    pub fn media_set_label(&self) -> &Option<MediaSetLabel> {
+        &self.id.media_set_label
+    }
+
+    /// Updates the media set label
+    pub fn set_media_set_label(&mut self, set_label: MediaSetLabel) {
+        self.id.media_set_label = Some(set_label);
+    }
+    
+    /// Returns the drive label
+    pub fn label(&self) -> &DriveLabel {
+        &self.id.label
+    }
+
+    /// Returns the media id (drive label + media set label)
+    pub fn id(&self) -> &MediaId {
+        &self.id
+    }
+
+    /// Returns the media label (Barcode)
+    pub fn changer_id(&self) -> &str {
+        &self.id.label.changer_id
+    }
+}
diff --git a/src/tape/mod.rs b/src/tape/mod.rs
index ac6802af..9bb6bb6e 100644
--- a/src/tape/mod.rs
+++ b/src/tape/mod.rs
@@ -31,6 +31,9 @@ pub use media_state_database::*;
 mod online_status_map;
 pub use online_status_map::*;
 
+mod media_pool;
+pub use media_pool::*;
+
 /// Directory path where we store all tape status information
 pub const TAPE_STATUS_DIR: &str = "/var/lib/proxmox-backup/tape";