From owner-freebsd-arch Thu Nov 2 19:39:19 2000 Delivered-To: freebsd-arch@freebsd.org Received: from earth.backplane.com (placeholder-dcat-1076843399.broadbandoffice.net [64.47.83.135]) by hub.freebsd.org (Postfix) with ESMTP id 220D837B4C5 for ; Thu, 2 Nov 2000 19:39:17 -0800 (PST) Received: (from dillon@localhost) by earth.backplane.com (8.11.1/8.9.3) id eA33d9D43976; Thu, 2 Nov 2000 19:39:09 -0800 (PST) (envelope-from dillon) Date: Thu, 2 Nov 2000 19:39:09 -0800 (PST) From: Matt Dillon Message-Id: <200011030339.eA33d9D43976@earth.backplane.com> To: Marius Bendiksen Cc: Alfred Perlstein , Randell Jesup , arch@freebsd.org Subject: Re: Like to commit my diskprep References: Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG : :> Indirect blocks aren't relevant if you are using a large block size, :> because there are few enough of them the OS has no problem caching :> them. : :The problem is related to highly random access, as the indirect blocks :will tend to get pushed out of the cache on occasion, requiring multiple :seeks when the file is being accessed. Using extents will solve this. : :> 32K block size 4MB : :Note that these 4MB are better spent on caching real data than they are on :compensating for the absence of extents in the FFS inode. :.. : :> It becomes somewhat more of an issue for a terrabyte-sized database, :> but still no biggy considering the memory you can get these days. : :I reiterate the above point. The kind of memory in question here is really :way over the top, compared to the 8/16 bytes required to hold an extent :reference and the bit to indicate that the inode uses such. : :Marius Lets put things into perspective here. You have a multi-gig or terrabyte database, and that pretty much means you have to at least a gig of ram in the machine that's going to be accessing it. Otherwise why bother with caching at all? If you have a machine with a gig of ram, losing 4MB is REALLY not a big deal. -Matt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message