mirror of
https://github.com/versity/scoutfs.git
synced 2026-09-08 09:07:30 +00:00
Zach Brown
847916860d
The move_blocks ioctl finds extents to move in the source file by searching from the starting block offset of the region to move. Logically, this is fine. After each extent item is deleted the next search will find the next extent. The problem is that deleted items still exist in the item cache. The next iteration has to skip over all the deleted extents from the start of the region. This is fine with large extents, but with heavily fragmented extents this creates a huge amplification of the number of items to traverse when moving the fragmented extents in a large file. (It's not quite O(n^2)/2 for the total extents, deleted items are purged as we write out the dirty items in each transaction.. but it's still immense.) The fix is to simply start searching for the next extent after the one we just moved. 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
Community Mailing List
Please join us on the open scoutfs-devel@scoutfs.org mailing list hosted on Google Groups