diff --git a/src/drivers/block/scsi.c b/src/drivers/block/scsi.c
index d51b5cfa..f765c976 100644
--- a/src/drivers/block/scsi.c
+++ b/src/drivers/block/scsi.c
@@ -40,6 +40,9 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  *
  */
 
+/** Maximum number of TEST UNIT READY retries */
+#define SCSI_READY_MAX_RETRIES 10
+
 /* Error numbers generated by SCSI sense data */
 #define EIO_NO_SENSE __einfo_error ( EINFO_EIO_NO_SENSE )
 #define EINFO_EIO_NO_SENSE \
@@ -240,6 +243,8 @@ struct scsi_device {
 	struct interface ready;
 	/** TEST UNIT READY process */
 	struct process process;
+	/** TEST UNIT READY retry count */
+	unsigned int retries;
 
 	/** List of commands */
 	struct list_head cmds;
@@ -875,20 +880,40 @@ static struct interface_descriptor scsidev_block_desc =
 static void scsidev_ready ( struct scsi_device *scsidev, int rc ) {
 
 	/* Shut down interface */
-	intf_shutdown ( &scsidev->ready, rc );
+	intf_restart ( &scsidev->ready, rc );
 
-	/* Close device on failure */
-	if ( rc != 0 ) {
-		DBGC ( scsidev, "SCSI %p not ready: %s\n",
-		       scsidev, strerror ( rc ) );
-		scsidev_close ( scsidev, rc );
+	/* Mark device as ready, if applicable */
+	if ( rc == 0 ) {
+		DBGC ( scsidev, "SCSI %p unit is ready\n", scsidev );
+		scsidev->flags |= SCSIDEV_UNIT_READY;
+		xfer_window_changed ( &scsidev->block );
+		return;
+	}
+	DBGC ( scsidev, "SCSI %p not ready: %s\n", scsidev, strerror ( rc ) );
+
+	/* SCSI targets have an annoying habit of returning occasional
+	 * pointless "error" messages such as "power-on occurred", so
+	 * we have to be prepared to retry commands.
+	 *
+	 * For most commands, we rely on the caller (e.g. the generic
+	 * SAN device layer) to retry commands as needed.  However, a
+	 * TEST UNIT READY failure is used as an indication that the
+	 * whole SCSI device is unavailable and should be closed.  We
+	 * must therefore perform this retry loop within the SCSI
+	 * layer.
+	 */
+	if ( scsidev->retries++ < SCSI_READY_MAX_RETRIES ) {
+		DBGC ( scsidev, "SCSI %p retrying (retry %d)\n",
+		       scsidev, scsidev->retries );
+		scsidev->flags &= ~SCSIDEV_UNIT_TESTED;
+		process_add ( &scsidev->process );
 		return;
 	}
 
-	/* Mark device as ready */
-	scsidev->flags |= SCSIDEV_UNIT_READY;
-	xfer_window_changed ( &scsidev->block );
-	DBGC ( scsidev, "SCSI %p unit is ready\n", scsidev );
+	/* Close device */
+	DBGC ( scsidev, "SCSI %p never became ready: %s\n",
+	       scsidev, strerror ( rc ) );
+	scsidev_close ( scsidev, rc );
 }
 
 /** SCSI device TEST UNIT READY interface operations */