Date: Fri, 09 Jan 2009 12:30:09 +1000 From: Danny Carroll <fbsd@dannysplace.net> To: Koen Smits <kgysmits@gmail.com> Cc: freebsd-fs@freebsd.org, Jeremy Chadwick <koitsu@freebsd.org>, freebsd-hardware@freebsd.org Subject: Re: Areca vs. ZFS performance testing. Message-ID: <4966B6B1.8020502@dannysplace.net> In-Reply-To: <b072dc420901072348n7d094937u89b6d24959f8ae3d@mail.gmail.com> References: <20081031033208.GA21220@icarus.home.lan> <490A8FAD.8060009@dannysplace.net> <491BBF38.9010908@dannysplace.net> <491C5AA7.1030004@samsco.org> <491C9535.3030504@dannysplace.net> <CEDCDD3E-B908-44BF-9D00-7B73B3C15878@anduin.net> <4920E1DD.7000101@dannysplace.net> <F55CD13C-8117-4D34-9C35-618D28F9F2DE@spry.com> <20081117070818.GA22231@icarus.home.lan> <496549D9.7010003@dannysplace.net> <b072dc420901072348n7d094937u89b6d24959f8ae3d@mail.gmail.com>
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Koen Smits wrote: > My guess is it probably has to do with the way ZFS does cache flushes: > http://www.solarisinternals.com/wiki/index.php/ZFS_Evil_Tuning_Guide#Cache_Flushes > It might be worth it to disable the forced flushing and test again, if > you feel like it. I've just done this and the results are on the same page: http://www.dannysplace.net/quickweb/filesystem%20tests.htm The Excel version is here: http://www.dannysplace.net/quickweb/filesystem%20tests.xls It is a major improvement but I do not know 100% for sure if the disks are protected by the write cache/battery backup when in Passthrough mode. When creating a passthrough disk the "Volume Cache Mode" can be set to "Write Back" or "Write Through". This makes me feel as though the cache is being used and that when the cache is used, so is the BBU. But I cannot be 100% sure. I will send an email to Areca support to ask. -D
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