Date: Thu, 17 Jan 2013 10:32:59 +0100 From: Nicolas Rachinsky <fbsd-mas-0@ml.turing-complete.org> To: Andriy Gapon <avg@FreeBSD.org> Cc: freebsd-fs <freebsd-fs@FreeBSD.org> Subject: Re: slowdown of zfs (tx->tx) Message-ID: <20130117093259.GA83951@mid.pc5.i.0x5.de> In-Reply-To: <50F69788.2040506@FreeBSD.org> References: <20130114195148.GA20540@mid.pc5.i.0x5.de> <CAFqOu6jwJ4qhbOovN_NhzusdQJvrbvUC3g93sziR=Uw99SGenw@mail.gmail.com> <20130114214652.GA76779@mid.pc5.i.0x5.de> <CAFqOu6jKX-Ks6C1RK5GwZ51ZVUSnGSe7S99_EfK%2BfwLPjAFFYw@mail.gmail.com> <20130115224556.GA41774@mid.pc5.i.0x5.de> <CAFqOu6jJnWdbikPmE1-UML5i_x7meF%2BiyY=9WBRyv2j7AeOaSg@mail.gmail.com> <50F67551.5020704@FreeBSD.org> <20130116095009.GA36867@mid.pc5.i.0x5.de> <FD780217EA4548F187715AF1AAF2B91A@multiplay.co.uk> <50F69788.2040506@FreeBSD.org>
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* Andriy Gapon <avg@FreeBSD.org> [2013-01-16 14:05 +0200]: > on 16/01/2013 12:14 Steven Hartland said the following: > > You only have ~11% free so yer it is pretty full ;-) > > just in case, Steve is not kidding. > > Those free hundreds of gigabytes could be spread over the terabytes and could be > quite fragmented if the pool has a history of adding and removing lots of files. > ZFS could be spending quite a lot of time in that case when it looks for some > free space and tries to minimize further fragmentation. > > Empirical/anecdotal safe limit on pool utilization is said to be about 70-80%. > > You can test if this guess is true by doing the following: > kgdb -w > (kgdb) set metaslab_min_alloc_size=4096 > > If performance noticeably improves after that, then this is your problem indeed. I tried this, but I didn't notice any difference in performance. Next I'll try the update Artem suggested. Thanks Nicolas -- http://www.rachinsky.de/nicolas
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