mirror of https://github.com/octoleo/restic.git
91 lines
4.3 KiB
ReStructuredText
91 lines
4.3 KiB
ReStructuredText
..
|
||
Normally, there are no heading levels assigned to certain characters as the structure is
|
||
determined from the succession of headings. However, this convention is used in Python’s
|
||
Style Guide for documenting which you may follow:
|
||
# with overline, for parts
|
||
* for chapters
|
||
= for sections
|
||
- for subsections
|
||
^ for subsubsections
|
||
" for paragraphs
|
||
|
||
########################
|
||
Tuning Backup Parameters
|
||
########################
|
||
|
||
Restic offers a few parameters that allow tuning the backup. The default values should
|
||
work well in general although specific use cases can benefit from different non-default
|
||
values. As the restic commands evolve over time, the optimal value for each parameter
|
||
can also change across restic versions.
|
||
|
||
|
||
Backend Connections
|
||
===================
|
||
|
||
Restic uses a global limit for the number of concurrent connections to a backend.
|
||
This limit can be configured using ``-o <backend-name>.connections=5``, for example for
|
||
the REST backend the parameter would be ``-o rest.connections=5``. By default restic uses
|
||
``5`` connections for each backend, except for the local backend which uses a limit of ``2``.
|
||
The defaults should work well in most cases. For high-latency backends it can be beneficial
|
||
to increase the number of connections. Please be aware that this increases the resource
|
||
consumption of restic and that a too high connection count *will degrade performance*.
|
||
|
||
|
||
CPU Usage
|
||
=========
|
||
|
||
By default, restic uses all available CPU cores. You can set the environment variable
|
||
`GOMAXPROCS` to limit the number of used CPU cores. For example to use a single CPU core,
|
||
use `GOMAXPROCS=1`. Limiting the number of usable CPU cores, can slightly reduce the memory
|
||
usage of restic.
|
||
|
||
|
||
Compression
|
||
===========
|
||
|
||
For a repository using at least repository format version 2, you can configure how data
|
||
is compressed with the option ``--compression``. It can be set to ``auto`` (the default,
|
||
which will compress very fast), ``max`` (which will trade backup speed and CPU usage for
|
||
slightly better compression), or ``off`` (which disables compression). Each setting is
|
||
only applied for the single run of restic. The option can also be set via the environment
|
||
variable ``RESTIC_COMPRESSION``.
|
||
|
||
|
||
File Read Concurrency
|
||
=====================
|
||
|
||
When backing up fast storage like NVME disks, it can be beneficial to increase the read
|
||
concurrency. This can increase the overall performance of the backup operation by reading
|
||
more files in parallel. You can specify the concurrency of file reads with the
|
||
``RESTIC_READ_CONCURRENCY`` environment variable or the ``--read-concurrency`` flag for
|
||
the ``backup`` command.
|
||
|
||
|
||
Pack Size
|
||
=========
|
||
|
||
In certain instances, such as very large repositories (in the TiB range) or very fast
|
||
upload connections, it is desirable to use larger pack sizes to reduce the number of
|
||
files in the repository and improve upload performance. Notable examples are OpenStack
|
||
Swift and some Google Drive Team accounts, where there are hard limits on the total
|
||
number of files. Larger pack sizes can also improve the backup speed for a repository
|
||
stored on a local HDD. This can be achieved by either using the ``--pack-size`` option
|
||
or defining the ``$RESTIC_PACK_SIZE`` environment variable. Restic currently defaults
|
||
to a 16 MiB pack size.
|
||
|
||
The side effect of increasing the pack size is requiring more disk space for temporary pack
|
||
files created before uploading. The space must be available in the system default temp
|
||
directory, unless overwritten by setting the ``$TMPDIR`` environment variable. In addition,
|
||
depending on the backend the memory usage can also increase by a similar amount. Restic
|
||
requires temporary space according to the pack size, multiplied by the number
|
||
of backend connections plus one. For example, if the backend uses 5 connections (the default
|
||
for most backends), with a target pack size of 64 MiB, you'll need a *minimum* of 384 MiB
|
||
of space in the temp directory. A bit of tuning may be required to strike a balance between
|
||
resource usage at the backup client and the number of pack files in the repository.
|
||
|
||
Note that larger pack files increase the chance that the temporary pack files are written
|
||
to disk. An operating system usually caches file write operations in memory and writes
|
||
them to disk after a short delay. As larger pack files take longer to upload, this
|
||
increases the chance of these files being written to disk. This can increase disk wear
|
||
for SSDs.
|