yahoo-eng-team team mailing list archive

[Matt Riedemann <mriedem.os@xxxxxxxxx>]

This isn't really a bug, and there is a blueprint for this with some
discussion:

https://blueprints.launchpad.net/nova/+spec/nova-improvement-of-maximum-
attach-volumes-more-than-26-vols

** Changed in: nova
       Status: New => Incomplete

** Changed in: nova
       Status: Incomplete => Opinion

** Changed in: nova
   Importance: Undecided => Wishlist

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https://bugs.launchpad.net/bugs/1773941

Title:
  Not able to attach more than 25 volumes using virtio-scsi

Status in OpenStack Compute (nova):
  Opinion

Bug description:
  Not able to attach more than 25 volumes using virtio-scsi

  In nova/virt/libvirt/blockinfo.py,

  def get_dev_count_for_disk_bus(disk_bus):
      """Determine the number disks supported.

         Determine how many disks can be supported in
         a single VM for a particular disk bus.

         Returns the number of disks supported.
      """

      if disk_bus == "ide":
          return 4
      else:
          return 26 <=== we're just responding with 26 devices that we can use.

  and

  
  def find_disk_dev_for_disk_bus(mapping, bus,
                                 last_device=False,
                                 assigned_devices=None):
      """Identify a free disk dev name for a bus.

         Determines the possible disk dev names for
         the bus, and then checks them in order until
         it identifies one that is not yet used in the
         disk mapping. If 'last_device' is set, it will
         only consider the last available disk dev name.

         Returns the chosen disk_dev name, or raises an
         exception if none is available.
      """

      dev_prefix = get_dev_prefix_for_disk_bus(bus)
      if dev_prefix is None:
          return None

      if assigned_devices is None:
          assigned_devices = []

      max_dev = get_dev_count_for_disk_bus(bus)
      if last_device:
          devs = [max_dev - 1]
      else:
          devs = range(max_dev)

      for idx in devs:
          disk_dev = dev_prefix + chr(ord('a') + idx)  <====== need to correct naming of devices
          if not has_disk_dev(mapping, disk_dev):
              if disk_dev not in assigned_devices:
                  return disk_dev

      raise exception.NovaException(
          _("No free disk device names for prefix '%s'") %
          dev_prefix)

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