mirror of https://github.com/schoebel/mars
112 lines
4.0 KiB
Plaintext
112 lines
4.0 KiB
Plaintext
You need the kernel sources for at least 2.6.32. Some elder versions
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may work, but we have not tested it.
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Currently, MARS Light builds only with 64bit kernels.
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Go to your linux source tree, and apply one of the pre-patches for MARS.
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You can find them in the subdirectory pre-patches/ of the MARS sources.
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These pre-patches are almost trivial, they contain only a few
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EXPORT_SYMBOL() statements. Porting to other kernel versions should
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be trivial.
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One of the pre-patches has been ported to an openvz kernel
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even by one of our sysadmins, who usually does no C programming.
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So this should be no major hurdle.
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Because of the need for some small pre-patches, we recommend to build
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MARS inside the kernel source tree (in-tree).
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If you are an experience sysadmin and want to build MARS as an external
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kernel module, you may try the Debian based scripts provided by our
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sysadmins. Be warned that you have to check yourself for source
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compatibility, the right compiler flags, etc; very nasty errors may
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appear if you fail to do so!
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Therefore, try the in-tree method first.
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For the in-tree build, you need to also apply one of the patches
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pre-patches/vanilla-*/*necessary-for-in-tree-build.patch
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or similar.
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Go to ${your_kernel_source}/block/ and clone the MARS git repository there.
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Then build your kernel as usual. You need to use 64bit. In addition, you
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need to enable the following options before MARS shows up at all:
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PROC_SYSCTL
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HIGH_RES_TIMERS
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Don't enable CONFIG_DEBUG_SG (this will currently not work until it is fixed).
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In Kconfig, you will find lots of additional options for MARS. Most
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of them should be left at their default. It suffices just to switch
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on MARS as a whole, and let it build as a single kernel module.
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If no Kconfig options for MARS show up in the in-tree build, you have
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probably forgotten to apply the appropriate
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pre-patches/vanilla-*/*necessary-for-in-tree-build.patch
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or similar.
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Finally, copy userspace/marsadm to some appropriate location in
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your $PATH.
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Do the following at both your primary and secondary node:
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After booting your pre-patched kernel, don't modprobe mars. Before
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that, create an empty filesystem with at least 100GB (ext4 is highly
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recommended; there seem to remain some recursion deadlock problems
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with xfs which will be hopefully fixed in the next time)
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and mount it to /mars/ .
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Additionally, you need an empty block device having exactly the same
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size at both nodes. In the following, they are called /dev/vg-x/myspace .
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On the primary:
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marsadm create-cluster
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On the secondary:
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marsadm join-cluster ${hostname_of_primary}
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Only after that, do on both nodes:
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modprobe mars
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On the primary:
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marsadm create-resource myspace /dev/vg-x/myspace
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Wait a few seconds until the state information about the new resource has
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spread over the whole cluster.
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On the secondary:
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marsadm join-resource myspace /dev/vg-x/myspace
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Shortly after that, the initial full sync should start automatically.
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On the primary, a device /dev/mars/myspace should appear, having exactly
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the same size as /dev/vg-x/myspace .
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Now you can use /dev/mars/myspace on the primary for creating a filesystem,
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mounting, or exporting via iSCSI, etc.
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From time to time, you should execute the following commands on one of
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your nodes:
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marsadm log-rotate all
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sleep 10
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marsadm log-delete-all all
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... in order to prevent your /mars/ filesystem from running full.
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hint: use cron jobs for automation.
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Most marsadm commands are very similar to drbdadm. Details can be
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found in docu/mars-user-manual.pdf. The sourcecode of marsadm is a very
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simple and stupid perl script, which intentionally does not use any
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perl module and no OO. The source code will tell you almost anything
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about the symlinks present in /mars/.
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If you are curious about how MARS replicates its state information
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over the network, just do the following on both nodes:
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watch ls -l /mars/resource-myspace/
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Alternatively / additionally, you may try Joerg's script mars-status.pl
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which will deliver colorful state reports from the practical viewpoint
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of an experienced sysadmin.
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