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
storage.config file the new settings will not be effective until Traffic Server is restarted.
The format of the
storage.config file is a series of lines of the form
pathname size [
volume=number ] [
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
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.
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.
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
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
As with standard
records.config integers, human readable prefixes are also
supported. They include
KKilobytes (1024 bytes)
MMegabytes (1024^2 or 1,048,576 bytes)
GGigabytes (1024^3 or 1,073,741,824 bytes)
TTerabytes (1024^4 or 1,099,511,627,776 bytes)
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 maintaing the mapping from physical device to base string even in the presence of hardware changes and failures.
The following basic example shows 128 MB of cache storage in the
You can use the
. symbol for the current directory. Here is an
example for 64 MB of cache storage in the current directory:
As an alternative, using the human readable prefixes, you can express a 64GB cache file with:
When using on-filesystem cache disk storage, you can only have one such directory specified. This will be address in a future version.
The following example is for the Solaris operating system:
Size is optional. If not specified, the entire partition is used.
Rather than refer to disk devices like
modern Linux supports alternative symlinked names for disk devices in the
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
/dev/disk. Note that if the
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
# 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
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:
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 tserver:tserver