Date: Fri, 16 Aug 2013 22:04:02 +0200 From: Willem Jan Withagen <wjw@digiware.nl> To: Karl Denninger <karl@denninger.net> Cc: fs@freebsd.org Subject: Re: Fwd: Disk scheduling activity... Message-ID: <520E85B2.8090500@digiware.nl> In-Reply-To: <520BA3EC.1030304@denninger.net> References: <520B8B1E.7060002@digiware.nl> <alpine.GSO.2.01.1308140859070.2267@freddy.simplesystems.org> <520BA249.8030603@digiware.nl> <520BA3EC.1030304@denninger.net>
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On 14-8-2013 17:36, Karl Denninger wrote: >> That would then be the Areca controller, bacause I have the feeling >> that it always writes later. >> >> --WjW >> _ > I very much doubt the ARECA is ignoring the cache-flush request. > > I have several of these and can get them into a pathological state with > TERRIBLE performance when ZFS starts doing things that demand cache > flushes - the ARECA will perform the demanded flush which, if you have a > lot of RAM on the board, gets real interesting in terms of performance > impact. I think my wording was what wrong. What I meant is that the Areca controller was "late" in writing because of the battery backupped cache. If it were to ignore cache-flushes that would make it not really a very good controller. Your remarks of getting the controller list in its workload are sort of worrisome.... --WjW
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