Date: Thu, 29 Jan 2009 15:48:48 +0100 (CET) From: Oliver Fromme <olli@lurza.secnetix.de> To: freebsd-current@FreeBSD.ORG, ptice@aldridge.com Subject: Re: Help me select hardware....Some real world data that might help Message-ID: <200901291448.n0TEmmiO061258@lurza.secnetix.de> In-Reply-To: <E8FEAE26C87DED4EB49EFF99D1C7A51DFF692F@ald-mail02.corporate.aldridge.com>
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Paul Tice wrote: > I just bumped up the kmem, arc.max, enabled zil and reenabled > mdcomp. Prefetch is disabled. Less than 1 minute into a backup > run of only 4 machines, I've got a fresh ZFS wedgie. How exactly did you bump up kmem? As far as I know, it is not necessary anymore on 8-current/amd64, because the defaults are already much larger. In fact it might be possible that your tuning made things worse. > As I understand it, the ZIL is not as much of an integrity boost as > a speed boost, especially since we already have checksum-per-block. The checksum feature works purely on a block level, while the intent log (ZIL) records certain changes to meta data on the file system, similar to a journal, which can be used for recovery after a crash (power outage, hardware failure, kernel panic, human error). Both features are completely orthogonal, one cannot replace the other. Therefore I recommend to keep the ZIL enabled. Best regards Oliver -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M. Handelsregister: Registergericht Muenchen, HRA 74606, Geschäftsfuehrung: secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün- chen, HRB 125758, Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd "In My Egoistical Opinion, most people's C programs should be indented six feet downward and covered with dirt." -- Blair P. Houghton
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