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author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-09 22:34:26 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-09 22:34:26 +0300 |
commit | e9a83bd2322035ed9d7dcf35753d3f984d76c6a5 (patch) | |
tree | 66dc466ff9aec0f9bb7f39cba50a47eab6585559 /Documentation/device-mapper/striped.rst | |
parent | 7011b7e1b702cc76f9e969b41d9a95969f2aecaa (diff) | |
parent | 454f96f2b738374da4b0a703b1e2e7aed82c4486 (diff) | |
download | linux-e9a83bd2322035ed9d7dcf35753d3f984d76c6a5.tar.xz |
Merge tag 'docs-5.3' of git://git.lwn.net/linux
Pull Documentation updates from Jonathan Corbet:
"It's been a relatively busy cycle for docs:
- A fair pile of RST conversions, many from Mauro. These create more
than the usual number of simple but annoying merge conflicts with
other trees, unfortunately. He has a lot more of these waiting on
the wings that, I think, will go to you directly later on.
- A new document on how to use merges and rebases in kernel repos,
and one on Spectre vulnerabilities.
- Various improvements to the build system, including automatic
markup of function() references because some people, for reasons I
will never understand, were of the opinion that
:c:func:``function()`` is unattractive and not fun to type.
- We now recommend using sphinx 1.7, but still support back to 1.4.
- Lots of smaller improvements, warning fixes, typo fixes, etc"
* tag 'docs-5.3' of git://git.lwn.net/linux: (129 commits)
docs: automarkup.py: ignore exceptions when seeking for xrefs
docs: Move binderfs to admin-guide
Disable Sphinx SmartyPants in HTML output
doc: RCU callback locks need only _bh, not necessarily _irq
docs: format kernel-parameters -- as code
Doc : doc-guide : Fix a typo
platform: x86: get rid of a non-existent document
Add the RCU docs to the core-api manual
Documentation: RCU: Add TOC tree hooks
Documentation: RCU: Rename txt files to rst
Documentation: RCU: Convert RCU UP systems to reST
Documentation: RCU: Convert RCU linked list to reST
Documentation: RCU: Convert RCU basic concepts to reST
docs: filesystems: Remove uneeded .rst extension on toctables
scripts/sphinx-pre-install: fix out-of-tree build
docs: zh_CN: submitting-drivers.rst: Remove a duplicated Documentation/
Documentation: PGP: update for newer HW devices
Documentation: Add section about CPU vulnerabilities for Spectre
Documentation: platform: Delete x86-laptop-drivers.txt
docs: Note that :c:func: should no longer be used
...
Diffstat (limited to 'Documentation/device-mapper/striped.rst')
-rw-r--r-- | Documentation/device-mapper/striped.rst | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/Documentation/device-mapper/striped.rst b/Documentation/device-mapper/striped.rst new file mode 100644 index 000000000000..e9a8da192ae1 --- /dev/null +++ b/Documentation/device-mapper/striped.rst @@ -0,0 +1,61 @@ +========= +dm-stripe +========= + +Device-Mapper's "striped" target is used to create a striped (i.e. RAID-0) +device across one or more underlying devices. Data is written in "chunks", +with consecutive chunks rotating among the underlying devices. This can +potentially provide improved I/O throughput by utilizing several physical +devices in parallel. + +Parameters: <num devs> <chunk size> [<dev path> <offset>]+ + <num devs>: + Number of underlying devices. + <chunk size>: + Size of each chunk of data. Must be at least as + large as the system's PAGE_SIZE. + <dev path>: + Full pathname to the underlying block-device, or a + "major:minor" device-number. + <offset>: + Starting sector within the device. + +One or more underlying devices can be specified. The striped device size must +be a multiple of the chunk size multiplied by the number of underlying devices. + + +Example scripts +=============== + +:: + + #!/usr/bin/perl -w + # Create a striped device across any number of underlying devices. The device + # will be called "stripe_dev" and have a chunk-size of 128k. + + my $chunk_size = 128 * 2; + my $dev_name = "stripe_dev"; + my $num_devs = @ARGV; + my @devs = @ARGV; + my ($min_dev_size, $stripe_dev_size, $i); + + if (!$num_devs) { + die("Specify at least one device\n"); + } + + $min_dev_size = `blockdev --getsz $devs[0]`; + for ($i = 1; $i < $num_devs; $i++) { + my $this_size = `blockdev --getsz $devs[$i]`; + $min_dev_size = ($min_dev_size < $this_size) ? + $min_dev_size : $this_size; + } + + $stripe_dev_size = $min_dev_size * $num_devs; + $stripe_dev_size -= $stripe_dev_size % ($chunk_size * $num_devs); + + $table = "0 $stripe_dev_size striped $num_devs $chunk_size"; + for ($i = 0; $i < $num_devs; $i++) { + $table .= " $devs[$i] 0"; + } + + `echo $table | dmsetup create $dev_name`; |