143 lines
4.0 KiB
ReStructuredText
143 lines
4.0 KiB
ReStructuredText
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Build & Release Notes
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*********************
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``rustup`` Toolchain
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====================
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We normally want to build with the ``rustc`` Debian package. To do that
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you can set the following ``rustup`` configuration:
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# rustup toolchain link system /usr
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# rustup default system
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Versioning of proxmox helper crates
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===================================
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To use current git master code of the proxmox* helper crates, add::
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git = "git://git.proxmox.com/git/proxmox"
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or::
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path = "../proxmox/proxmox"
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to the proxmox dependency, and update the version to reflect the current,
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pre-release version number (e.g., "0.1.1-dev.1" instead of "0.1.0").
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Local cargo config
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==================
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This repository ships with a ``.cargo/config.toml`` that replaces the crates.io
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registry with packaged crates located in ``/usr/share/cargo/registry``.
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A similar config is also applied building with dh_cargo. Cargo.lock needs to be
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deleted when switching between packaged crates and crates.io, since the
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checksums are not compatible.
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To reference new dependencies (or updated versions) that are not yet packaged,
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the dependency needs to point directly to a path or git source (e.g., see
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example for proxmox crate above).
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Build
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=====
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on Debian 12 Bookworm
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Setup:
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1. # echo 'deb http://download.proxmox.com/debian/devel/ bookworm main' | sudo tee /etc/apt/sources.list.d/proxmox-devel.list
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2. # sudo wget https://enterprise.proxmox.com/debian/proxmox-release-bookworm.gpg -O /etc/apt/trusted.gpg.d/proxmox-release-bookworm.gpg
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3. # sudo apt update
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4. # sudo apt install devscripts debcargo clang
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5. # git clone git://git.proxmox.com/git/proxmox-backup.git
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6. # cd proxmox-backup; sudo mk-build-deps -ir
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Note: 2. may be skipped if you already added the PVE or PBS package repository
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You are now able to build using the Makefile or cargo itself, e.g.::
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# make deb
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# # or for a non-package build
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# cargo build --all --release
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Design Notes
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************
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Here are some random thought about the software design (unless I find a better place).
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Large chunk sizes
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=================
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It is important to notice that large chunk sizes are crucial for performance.
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We have a multi-user system, where different people can do different operations
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on a datastore at the same time, and most operation involves reading a series
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of chunks.
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So what is the maximal theoretical speed we can get when reading a series of
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chunks? Reading a chunk sequence need the following steps:
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- seek to the first chunk's start location
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- read the chunk data
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- seek to the next chunk's start location
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- read the chunk data
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- ...
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Lets use the following disk performance metrics:
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:AST: Average Seek Time (second)
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:MRS: Maximum sequential Read Speed (bytes/second)
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:ACS: Average Chunk Size (bytes)
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The maximum performance you can get is::
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MAX(ACS) = ACS /(AST + ACS/MRS)
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Please note that chunk data is likely to be sequential arranged on disk, but
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this it is sort of a best case assumption.
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For a typical rotational disk, we assume the following values::
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AST: 10ms
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MRS: 170MB/s
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MAX(4MB) = 115.37 MB/s
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MAX(1MB) = 61.85 MB/s;
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MAX(64KB) = 6.02 MB/s;
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MAX(4KB) = 0.39 MB/s;
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MAX(1KB) = 0.10 MB/s;
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Modern SSD are much faster, lets assume the following::
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max IOPS: 20000 => AST = 0.00005
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MRS: 500Mb/s
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MAX(4MB) = 474 MB/s
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MAX(1MB) = 465 MB/s;
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MAX(64KB) = 354 MB/s;
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MAX(4KB) = 67 MB/s;
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MAX(1KB) = 18 MB/s;
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Also, the average chunk directly relates to the number of chunks produced by
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a backup::
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CHUNK_COUNT = BACKUP_SIZE / ACS
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Here are some staticics from my developer worstation::
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Disk Usage: 65 GB
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Directories: 58971
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Files: 726314
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Files < 64KB: 617541
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As you see, there are really many small files. If we would do file
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level deduplication, i.e. generate one chunk per file, we end up with
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more than 700000 chunks.
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Instead, our current algorithm only produce large chunks with an
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average chunks size of 4MB. With above data, this produce about 15000
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chunks (factor 50 less chunks).
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