> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss- > boun...@opensolaris.org] On Behalf Of Edward Ned Harvey > > New problem: > > I'm following all the advice I summarized into the OP of this thread, and > testing on a test system. (A laptop). And it's just not working. I am > jumping into the dedup performance abyss far, far eariler than predicted...
Now I'm repeating all these tests on a system that more closely resembles a server. This is a workstation with 6 core processor, 16G ram, and a single 1TB hard disk. In the default configuration, arc_meta_limit is 3837MB. And as I increase the number of unique blocks in the data pool, it is perfectly clear that performance jumps off a cliff when arc_meta_used starts to reach that level, which is approx 880,000 to 1,030,000 unique blocks. FWIW, this means, without evil tuning, a 16G server is only sufficient to run dedup on approx 33GB to 125GB unique data without severe performance degradation. I'm calling "severe degradation" anything that's an order of magnitude or worse. (That's 40K average block size * 880,000 unique blocks, and 128K average block size * 1,030,000 unique blocks.) So clearly this needs to be addressed, if dedup is going to be super-awesome moving forward. But I didn't quit there. So then I tweak the arc_meta_limit. Set to 7680MB. And repeat the test. This time, the edge of the cliff is not so clearly defined, something like 1,480,000 to 1,620,000 blocks. But the problem is - arc_meta_used never even comes close to 7680MB. At all times, I still have at LEAST 2G unused free mem. I have 16G physical mem, but at all times, I always have at least 2G free. my arcstats:c_max is 15G. But my arc size never exceeds 8.7G my arc_meta_limit is 7680 MB, but my arc_meta_used never exceeds 3647 MB. So what's the holdup? All of the above is, of course, just a summary. If you want complete overwhelming details, here they are: http://dl.dropbox.com/u/543241/dedup%20tests/readme.txt http://dl.dropbox.com/u/543241/dedup%20tests/datagenerate.c http://dl.dropbox.com/u/543241/dedup%20tests/getmemstats.sh http://dl.dropbox.com/u/543241/dedup%20tests/parse.py http://dl.dropbox.com/u/543241/dedup%20tests/runtest.sh http://dl.dropbox.com/u/543241/dedup%20tests/work%20workstation/runtest-outp ut-1st-pass.txt http://dl.dropbox.com/u/543241/dedup%20tests/work%20workstation/runtest-outp ut-1st-pass-parsed.xlsx http://dl.dropbox.com/u/543241/dedup%20tests/work%20workstation/runtest-outp ut-2nd-pass.txt http://dl.dropbox.com/u/543241/dedup%20tests/work%20workstation/runtest-outp ut-2nd-pass-parsed.xlsx _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
