Sergey E. Kolesnikov posted on Fri, 18 Apr 2014 21:07:00 +0400 as excerpted: > I've recently rebalanced my btrfs (kernel 3.13) running on two SSD > drives (raid-0) and a question arose. > Does btrfs perform TRIM on SSD balance? Fs is mounted with 'ssd' option, > but not 'discard'. > > It seems fstrim only trims free chunks in allocated space, so we > possibly having a "trim leak" if no special treatment is taken on blocks > reallocated during balance operation. As a user and list-regular, I don't know the answer to your question as I've not seen it come up before and don't recall seeing it covered on the wiki or the like either, but you have a very good point... and question. FWIW I'm on dual-physical-device-SSDs here too (tho on btrfs raid1 mainly because I like having a second copy of everything to restore from in case the one copy goes bad and fails checksum) and also don't use the discard option. While I'm currently running nearly 50% overprovisioned and thus the FTL has plenty of space to do its thing regardless of what I do with trim on the actually partitioned space, you raise a very good question indeed, one I wish I had thought to ask myself, and now that you have, one I'd very much like an answer to as well. =:^) -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
