>>>>> "ag" == Andreas Gustafsson <gson%gson.org@localhost> writes: ag> log-structured file system ... such a perfect match for solid ag> state disks JFFS2 in Linux is an LFS used for NOR flash, and it's mature and works well for them in many delivered products. like, it is a real LFS with a garbage collector and stuff. It's not suitable for SSD because it has O(n) mount time and keeps O(n) data in RAM such that it's basically useless beyond about 0.5GB, but aside from that you may find their experience relevant. They use no write buffer at all for JFFS2, but their current work (ubi/ubifs) does have a write cache. They are interested in running above raw NOR flash (and for their current work, raw NAND), so they are worried about wear-leveling now and about read-disturb and scrubbing for the future, which probably doesn't apply to SSD's with controllers. For SSD you cannot evade the proprietary wear-levelling software in the drive's controller, so the more interesting goal would be an access pattern that doesn't make drives get ``fragmented'' and degrade their performance. I've no idea how to do that. It may take a while since we can't see the software inside the drive, and the vendors won't want to give specifics about the problem unless you wring it out of them because they want people to think about it as little as possible.
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