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Zach Brown
5507ee5351
We don't directly mount the underlying devices for each mount because the kernel notices multiple mounts and doesn't setup a new super block for each. Previously the script used loopback devices to create the local shared block construct 'cause it was easy. This introduced corruption of blocks that saw concurrent read and write IOs. The buffered kernel file IO paths that loopback eventually degrades into by default (via splice) could have buffered readers copying out of pages without the page lock while writers modified the page. This manifest as occasional crc failure of blocks that we knowingly issue concurrent reads and writes to from multiple mounts (the quorum and super blocks). This changes the script to use device-mapper linear passthrough devices. Their IOs don't hit a caching layer and don't provide an opportunity to corrupt blocks. Signed-off-by: Zach Brown <zab@versity.com>
Introduction
scoutfs is a clustered in-kernel Linux filesystem designed to support large archival systems. It features additional interfaces and metadata so that archive agents can perform their maintenance workflows without walking all the files in the namespace. Its cluster support lets deployments add nodes to satisfy archival tier bandwidth targets.
The design goal is to reach file populations in the trillions, with the archival bandwidth to match, while remaining operational and responsive.
Highlights of the design and implementation include:
- Fully consistent POSIX semantics between nodes
- Atomic transactions to maintain consistent persistent structures
- Integrated archival metadata replaces syncing to external databases
- Dynamic seperation of resources lets nodes write in parallel
- 64bit throughout; no limits on file or directory sizes or counts
- Open GPLv2 implementation
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