NAME

       storage.config - Traffic Server cache storage configuration file

       The  storage.config  file (by default, located in /usr/local/etc/trafficserver/) lists all
       the files, directories, and/or hard disk partitions that make up the Traffic Server cache.
       After  you  modify  the  storage.config  file the new settings will not be effective until
       Traffic Server is restarted.

FORMAT

       The format of the storage.config file is a series of lines of the form
          pathname size [ volume=number ] [ id=string ]

       where pathname is the name of a partition, directory or file, size  is  the  size  of  the
       named partition, directory or file (in bytes), and volume is the volume number used in the
       files volume.config and hosting.config. id is used for seeding the Assignment  Table.  You
       must specify a size for directories; size is optional for files and raw partitions. volume
       and arg:seed are optional.

       NOTE:
          The volume option is independent of the seed option and either  can  be  used  with  or
          without the other, and their ordering on the line is irrelevant.

       NOTE:
          If the id option is used every use must have a unique value for string.

       You can use any partition of any size. For best performance:

       • Use raw disk partitions.

       • For each disk, make all partitions the same size.

       • For each node, use the same number of partitions on all disks.

       • Group  similar  kinds  of storage into different volumes. For example split out SSD's or
         RAM drives into their own volume.

       Specify pathnames according to your  operating  system  requirements.  See  the  following
       examples. In the storage.config file, a formatted or raw disk must be at least 128 MB.

       When  using  raw  disk or partitions, you should make sure the Traffic Server user used by
       the Traffic Server process has read and  write  privileges  on  the  raw  disk  device  or
       partition.  One  good  practice is to make sure the device file is set with 'g+rw' and the
       Traffic Server user is in the group which owns the device file.  However,  some  operating
       systems have stronger requirements - see the following examples for more information.

       As with standard records.config integers, human readable prefixes are also supported. They
       include

          • K Kilobytes (1024 bytes)

          • M Megabytes (1024^2 or 1,048,576 bytes)

          • G Gigabytes (1024^3 or 1,073,741,824 bytes)

          • T Terabytes (1024^4 or 1,099,511,627,776 bytes)

   Assignment Table
       Each storage element defined in storage.config is divided in to  stripes.  The  assignment
       table  maps  from  an object URL to a specific stripe. The table is initialized based on a
       pseudo-random process which is seeded by hashing a string for each stripe. This string  is
       composed of a base string, an offset (the start of the stripe on the storage element), and
       the length of the stripe. By default the path for the storage is used as the base  string.
       This  ensures that each stripe has a unique string for the assignment hash. This does make
       the assignment table very sensitive to the path for the storage elements and changing even
       one  can  have a cascading effect which will effectively clear most of the cache. This can
       be problem when drives fail and a system reboot causes the path names to change.

       The id option can be used to create a fixed string that an administrator can use  to  keep
       the  assignment  table  consistent by maintaining the mapping from physical device to base
       string even in the presence of hardware changes and failures.

EXAMPLES

       The following basic example shows 128 MB of cache storage in the /big_dir directory:

          /big_dir 134217728

       You can use the . symbol for the current directory. Here is an example for 64 MB of  cache
       storage in the current directory:

          . 134217728

       As  an  alternative,  using the human readable prefixes, you can express a 64GB cache file
       with:

          /really_big_dir 64G

       NOTE:
          When using on-filesystem cache disk storage, you  can  only  have  one  such  directory
          specified. This will be addressed in a future version.

   Solaris Example
       The following example is for the Solaris operating system:

          /dev/rdsk/c0t0d0s5
          /dev/rdsk/c0t0d1s5

       NOTE:
          Size is optional. If not specified, the entire partition is used.

   Linux Example
       NOTE:
          Rather  than refer to disk devices like /dev/sda, /dev/sdb, etc., modern Linux supports
          alternative symlinked names for disk devices in the /dev/disk directory  structure.  As
          noted  for  the  Assignment Table the path used for the disk can effect the cache if it
          changes. This can be ameloriated in some cases by using one of the alternate  paths  in
          via  /dev/disk.  Note  that  if  the by-id or by-path style is used, replacing a failed
          drive will cause that path to change because  the  new  drive  will  have  a  different
          physical ID or path. The original hash string can be kept by adding id or path with the
          original path to the storage line.

          If this is not sufficient then the id or path argument should be used to create a  more
          permanent assignment table. An example would be:

              /dev/sde id=cache.disk.0
              /dev/sdg id=cache.disk.1

       The following example will use an entire raw disk in the Linux operating system:

          /dev/disk/by-id/[DiskA_ID]    volume=1
          /dev/disk/by-path/[DiskB_Path]   volume=2

       In  order to make sure traffic_server will have access to this disk you can use udev(7) to
       persistently set the right permissions. The following rules are  targeted  for  an  Ubuntu
       system, and stored in /etc/udev/rules.d/51-cache-disk.rules:

          # Assign DiskA and DiskB to the tserver group
          # make the assignment final, no later changes allowed to the group!
          SUBSYSTEM=="block", KERNEL=="sd[ef]", GROUP:="tserver"

       In order to apply these settings, trigger a reload with udevadm(8)::

          udevadm trigger --subsystem-match=block

   FreeBSD Example
       Starting with 5.1 FreeBSD dropped support for explicit raw devices. All devices on FreeBSD
       can be accessed raw now.

       The following example will use an entire raw disk in the FreeBSD operating system:

          /dev/ada1
          /dev/ada2

       In order to make sure traffic_server will have access to this disk you can use devfs(8) to
       persistently set the right permissions. The following rules are stored in devfs.conf(5):

          # Assign /dev/ada1 and /dev/ada2 to the tserver user
          own    ada[12]  tserver:tserver

   Advanced
       Because  relative  paths  in  storage.config  are  relative to the base prefix, when using
       customized runroot it may be necessary to adjust such paths in  storage.config  or  adjust
       runroot.yaml itself.  Despite the name, the cachedir value is not used for this file.

COPYRIGHT

       2020, dev@trafficserver.apache.org