diff options
author | Thomas Waldmann <tw@waldmann-edv.de> | 2015-08-15 15:45:15 +0200 |
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committer | Thomas Waldmann <tw@waldmann-edv.de> | 2015-08-15 15:45:15 +0200 |
commit | 1d16e7a37c74aa965772b0867f0277d2aca08388 (patch) | |
tree | 7cba1a0c7d4e9421a7b450b32f562f22f7366f09 /docs | |
parent | bf757738f7a2b4d86e06aefd9b9f8bdda38e782d (diff) |
compression: update / refine docs
Diffstat (limited to 'docs')
-rw-r--r-- | docs/internals.rst | 18 | ||||
-rw-r--r-- | docs/quickstart.rst | 6 | ||||
-rw-r--r-- | docs/support.rst | 3 | ||||
-rw-r--r-- | docs/usage.rst | 3 |
4 files changed, 22 insertions, 8 deletions
diff --git a/docs/internals.rst b/docs/internals.rst index 0ea68098b..845dff131 100644 --- a/docs/internals.rst +++ b/docs/internals.rst @@ -386,19 +386,29 @@ Compression - none (no compression, pass through data 1:1) - lz4 (low compression, but super fast) -- zlib (level 1-9, level 1 is low, level 9 is high compression) -- lzma (level 0-9, level 0 is low, level 9 is high compression. +- zlib (level 0-9, level 0 is no compression [but still adding zlib overhead], + level 1 is low, level 9 is high compression) +- lzma (level 0-9, level 0 is low, level 9 is high compression). Speed: none > lz4 > zlib > lzma Compression: lzma > zlib > lz4 > none +Be careful, higher zlib and especially lzma compression levels might take a +lot of resources (CPU and memory). + The overall speed of course also depends on the speed of your target storage. If that is slow, using a higher compression level might yield better overall performance. You need to experiment a bit. Maybe just watch your CPU load, if that is relatively low, increase compression until 1 core is 70-100% loaded. -Be careful, higher zlib and especially lzma compression levels might take a -lot of resources (CPU and memory). +Even if your target storage is rather fast, you might see interesting effects: +while doing no compression at all (none) is a operation that takes no time, it +likely will need to store more data to the storage compared to using lz4. +The time needed to transfer and store the additional data might be much more +than if you had used lz4 (which is super fast, but still might compress your +data about 2:1). This is assuming your data is compressible (if you backup +already compressed data, trying to compress them at backup time is usually +pointless). Compression is applied after deduplication, thus using different compression methods in one repo does not influence deduplication. diff --git a/docs/quickstart.rst b/docs/quickstart.rst index 9abe4fb6a..4b78fefbb 100644 --- a/docs/quickstart.rst +++ b/docs/quickstart.rst @@ -101,11 +101,13 @@ If you have a quick repo storage and you want a little compression: $ borg create --compression lz4 /mnt/backup::repo ~ -If you have a medium fast repo storage and you want a bit more compression (N=0..9): +If you have a medium fast repo storage and you want a bit more compression (N=0..9, +0 means no compression, 9 means high compression): $ borg create --compression zlib,N /mnt/backup::repo ~ -If you have a very slow repo storage and you want high compression (N=0..9): +If you have a very slow repo storage and you want high compression (N=0..9, 0 means +low compression, 9 means high compression): $ borg create --compression lzma,N /mnt/backup::repo ~ diff --git a/docs/support.rst b/docs/support.rst index 5e953f202..f53c01285 100644 --- a/docs/support.rst +++ b/docs/support.rst @@ -4,6 +4,9 @@ Support ======= +Please first read the docs and the FAQ section in the docs, a lot of stuff is +documented / explained there. + Issue Tracker ------------- diff --git a/docs/usage.rst b/docs/usage.rst index a68d67c3f..c4e2fa80f 100644 --- a/docs/usage.rst +++ b/docs/usage.rst @@ -76,8 +76,7 @@ Resource Usage |project_name| might use a lot of resources depending on the size of the data set it is dealing with. CPU: it won't go beyond 100% of 1 core as the code is currently single-threaded. - Especially higher zlib and lzma compression uses significant amounts of CPU - cycles. + Especially higher zlib and lzma compression levels use significant amounts of CPU cycles. Memory (RAM): the chunks index and the files index are read into memory for performance reasons. compression, esp. lzma compression with high levels might need substantial amounts |