tape: add estimated medium wearout to status

src/api2/types/tape/drive.rs

@@ -204,4 +204,7 @@ pub struct LinuxDriveAndMediaStatus {
     /// the head.
     #[serde(skip_serializing_if="Option::is_none")]
     pub medium_passes: Option<u64>,
+    /// Estimated tape wearout factor (assuming max. 16000 end-to-end passes)
+    #[serde(skip_serializing_if="Option::is_none")]
+    pub medium_wearout: Option<f64>,
 }

src/bin/proxmox-tape.rs

@@ -696,6 +696,13 @@ fn status(
         _ => unreachable!(),
     };
 
+    let render_percentage = |value: &Value, _record: &Value| {
+        match value.as_f64() {
+            Some(wearout) => Ok(format!("{:.2}%", wearout*100.0)),
+            None => Ok(String::from("ERROR")), // should never happen
+        }
+    };
+
     let options = default_table_format_options()
         .column(ColumnConfig::new("blocksize"))
         .column(ColumnConfig::new("density"))
@@ -707,6 +714,7 @@ fn status(
         .column(ColumnConfig::new("bytes-written").renderer(render_bytes_human_readable))
         .column(ColumnConfig::new("bytes-read").renderer(render_bytes_human_readable))
         .column(ColumnConfig::new("medium-passes"))
+        .column(ColumnConfig::new("medium-wearout").renderer(render_percentage))
         .column(ColumnConfig::new("volume-mounts"))
         ;
 

src/tape/drive/linux_tape.rs

@@ -261,6 +261,7 @@ impl LinuxTapeHandle {
             bytes_read: None,
             bytes_written: None,
             medium_passes: None,
+            medium_wearout: None,
             volume_mounts: None,
         };
 
@@ -276,10 +277,17 @@ impl LinuxTapeHandle {
 
                 if let Ok(volume_stats) = self.volume_statistics() {
 
-                    status.medium_passes = Some(std::cmp::max(
+                    let passes = std::cmp::max(
                         volume_stats.beginning_of_medium_passes,
                         volume_stats.middle_of_tape_passes,
-                    ));
+                    );
+
+                    // assume max. 16000 medium passes
+                    // see: https://en.wikipedia.org/wiki/Linear_Tape-Open
+                    let wearout: f64 = (passes as f64)/(16000.0 as f64);
+
+                    status.medium_passes = Some(passes);
+                    status.medium_wearout = Some(wearout);
 
                     status.volume_mounts = Some(volume_stats.volume_mounts);
                 }