Bcache is a patch to use SSDs to transparently cache arbitrary block devices. Its main claim to fame is that it's designed for the performance characteristics of SSDs - it avoids random writes and extraneous IO at all costs, instead allocating buckets sized to your erase blocks and filling them up seqentially. It uses a hybrid btree/log, instead of a hash table as some other caches. It does both writethrough and writeback caching - it can use most of your SSD for buffering random writes, which are then flushed sequentially to the backing device. Skips sequential IO, too. Bcache currently looks suitable for noncritical use; don't throw it on your server without testing your specific configuration with it but the risk of data corruption is minimal. --- Since the last patch, there hasn't been a huge amount of user visible stuff. Much of the recent work has been on making memory allocation deadlock proof, which is mostly done at this point. Replaced some changes to the bio code with a different less intrusive way of doing things - this previously caused problems for btrfs and raid5 (as they used bios without calling bio_init() on them each time). The userspace interface has been changed a bit more: /sys/kernel/bcache moves to /sys/kernel/config/bcache, and attaching a cache to a backing device is now done more explicitly - see Documentation/bcache.txt. This will be the last version based on 2.6.35, next on my todo list is syncing up with mainline. All that's left before I'll consider it ready for mainline is replacing the hooks for transparent caching with something else; I'm hoping to be able to submit it by the next merge window but that could turn out to be pure fantasy... I was previously working on a device mapper interface to replace said transparent caching, but I'm giving up on that - dm just looks too unsuited to bcache's needs. If someone who knows the dm code better felt like taking a stab at it I'll be happy to help (and they should have an easy time of it, I got it minimally working) but I'm going to be doing something else. Further off, once the new block interface is done I'll be starting on thin provisioning, then tiered storage and multiple cache devices. As part of thin provisioning, bcache will be getting logical volume management. I'm perfectly happy to work with anyone else who's interested on interfaces, userspace and otherwise. Bcache is available from git://evilpiepirate.org/~kent/linux-bcache.git git://evilpiepirate.org/~kent/bcache-tools.git http://bcache.evilpiepirate.org Documentation/ABI/testing/sysfs-block-bcache | 156 + Documentation/bcache.txt | 178 + block/Kconfig | 16 + block/Makefile | 4 + block/bcache.c | 5505 ++++++++++++++++++++++++++ block/bcache_util.c | 78 + block/bcache_util.h | 306 ++ block/blk-core.c | 7 +- include/linux/bio.h | 1 + include/linux/blkdev.h | 1 + include/linux/fs.h | 5 + include/linux/sched.h | 4 + kernel/fork.c | 3 + 13 files changed, 6262 insertions(+), 2 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
