Date: Mon, 09 May 2016 14:25:54 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 209396] ZFS primarycache attribute affects secondary cache as well Message-ID: <bug-209396-8@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D209396 Bug ID: 209396 Summary: ZFS primarycache attribute affects secondary cache as well Product: Base System Version: 10.3-RELEASE Hardware: Any OS: Any Status: New Severity: Affects Only Me Priority: --- Component: kern Assignee: freebsd-bugs@FreeBSD.org Reporter: noah.bergbauer@tum.de # zpool create testpool gpt/test0 cache gpt/test1 # zpool list -v testpool NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH=20 ALTROOT testpool 1,98G 248K 1,98G - 0% 0% 1.00x ONLINE - gpt/test0 1,98G 248K 1,98G - 0% 0% cache - - - - - - gpt/test1 2,00G 36K 2,00G - 0% 0% # zfs create -o compression=3Doff testpool/testset # zfs set mountpoint=3D/testset testpool/testset # dd if=3D/dev/zero of=3D/testset/test.bin bs=3D1M count=3D1K 1024+0 records in 1024+0 records out 1073741824 bytes transferred in 10.510661 secs (102157401 bytes/sec) # zpool list -v testpool NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH=20 ALTROOT testpool 1,98G 1011M 1021M - 33% 49% 1.00x ONLINE - gpt/test0 1,98G 1011M 1021M - 33% 49% cache - - - - - - gpt/test1 2,00G 1010M 1,01G - 0% 49% So far so good: The data was written both to the actual pool and to the cac= he device. But what if we want to cache this huge file only in L2ARC and not in memory? # zfs set primarycache=3Dmetadata testpool/testset # zfs get secondarycache testpool/testset NAME PROPERTY VALUE SOURCE testpool/testset secondarycache all default # dd if=3D/testset/test.bin of=3D/dev/null bs=3D1M 1024+0 records in 1024+0 records out 1073741824 bytes transferred in 0.182155 secs (5894663608 bytes/sec) Still working as expected: This read was (obviously) serviced straight from= RAM because setting primarycache didn't immediately drop the cache. However, touching it with this read should cause the data to get evicted from ARC. # zpool list -v testpool NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH=20 ALTROOT testpool 1,98G 1,00G 1006M - 33% 50% 1.00x ONLINE - gpt/test0 1,98G 1,00G 1006M - 33% 50% cache - - - - - - gpt/test1 2,00G 556K 2,00G - 0% 0% # dd if=3D/testset/test.bin of=3D/dev/null bs=3D1M 1024+0 records in 1024+0 records out 1073741824 bytes transferred in 8.518173 secs (126053066 bytes/sec) The speed shows that this read came from disk, which is expected because RAM caching is now disabled. What's not expected is that the data was removed f= rom the cache device as well. No matter the workload (sequential/random), ZFS w= ill no longer utilize L2ARC for this dataset even though secondarycache is set = to all. There is *some* IO still going on, so perhaps it's still caching some metadata as this is what primarycache is set to. Note that I modified some sysctls to speed up cache warming for this test: vfs.zfs.l2arc_norw: 0 vfs.zfs.l2arc_feed_again: 1 vfs.zfs.l2arc_noprefetch: 0 vfs.zfs.l2arc_feed_secs: 0 vfs.zfs.l2arc_write_max: 1000000000000 --=20 You are receiving this mail because: You are the assignee for the bug.=
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