The Aurora Single Level Store provides transparent persistence for applications based on lightning fast incremental checkpoints. Aurora checkpoints are either stored on-disk in a custom object store or in memory for debugging applications. Unlike older single level stores Aurora provides a file system namespace into the store to enable backwards compatibility.
Applications can use the single level store API provided libsls to achieve higher performance and control Aurora's behavior.
The file tree is the following:
| Directories | Contents |
|---|---|
| benchmarks/ | Performance benchmarks |
| dtrace/ | DTrace scripts for debugging and performance measurements |
| include/ | Headers for userspace and the kernel |
| sls/ | Single Level Store in memory module |
| libsls/ | Userspace library implementing the API |
| scripts/ | Bash utilities for using Aurora and performance benchmarks |
| slfs/ | VFS filesystem for using files with Aurora |
| slos/ | Object Store backing Aurora |
| tests/ | Correctness tests for Aurora |
| tools/ | Userspace tools |
Dependencies:
- FreeBSD 12.3 with Aurora patches
- pidof (testbench)
Before you begin you must install and configure FreeBSD 12.3 with the Aurora enabling patches that can be done from our tree or a provided iso image. The build depends on header changes to FreeBSD and one of four provided kernel configuration files: GENERIC, PERF, FASTDBG, SLOWDBG.
WARNING: If you are building FreeBSD 12.3 with our patches please remember to do so on top of an existing FreeBSD 12.3 system.
# make
Once complete you may install Aurora using the following commands. Remember
that the newly installed commands newfs_sls and slsctl will not be in your
path until you type rehash.
# mkdir -p /usr/lib/debug/boot/modules
# mkdir -p /usr/lib/debug/sbin
# mkdir -p /usr/aurora/tests
# make install
The basic test suite can be run to verify things are working:
# cd tests
# ./testbench
Please note that testbenches are prefixed with project names. Disabled testbenches are often from other projects.
First you will want to load the kernel modules sls.ko and slos.ko that
provide the single level store and object store/file system functionality.
This will recursively load all dependent kernel modules.
# kldload sls
Next you will want to create a SLS object store on a flash storage device, we
use /dev/nvd0 the first NVMe disk as an example. You may specify any disk or
partition available to you.
WARNING: This will destroy all data on the device /dev/nvd0.
# newfs_sls /dev/nvd0
Finally we can mount the file system in a directory /aurora for our example.
This is an important step as this both mounts the file system and opens the
object store for use by the single level store. At the moment you may only
have a single aurora file system attached.
# mkdir /aurora
# mount -t slfs /dev/nvd0 /aurora
To manage the single level store you can use the slsctl command to attach
processes and create manual checkpoints. The system actually lets you create
partitions that are a logical grouping of persistent processes that can be
either memory backed or storage backed see the -m flag and -o flag. We
will only cover the most basic usage here.
To make an existing process persistent you use the attach command.
# slsctl attach -p <Process PID>
You can manually checkpoint the application using checkpoint. The -r flag
will recursively checkpoint all children of the parent process.
slsctl checkpoint [-r]
You can restore a process after a system crash using the restore command.
slsctl restore
- Emil Tsalapatis, Ryan Hancock, Tavian Barnes, Ali José Mashtizadeh. The Aurora Operating System: Revisiting the Single Level Store. In Proceedings of the 18th Workshop on Hot Topics in Operating Systems (HotOS ‘21). June, 2021.
- Emil Tsalapatis, Ryan Hancock, Tavian Barnes, Ali José Mashtizadeh. The Aurora Single Level Store Operating System In Proceedings of the 28th ACM Symposium on Operating Systems Principles (SOSP ‘21). September, 2021.