From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mea.tmt.tele.fi (mea.tmt.tele.fi [194.252.70.162]) by kvack.org (8.8.7/8.8.7) with ESMTP id SAA06598 for ; Tue, 25 May 1999 18:18:44 -0400 Subject: Re: Q: PAGE_CACHE_SIZE? In-Reply-To: from Rik van Riel at "May 25, 99 10:16:34 pm" Date: Wed, 26 May 1999 01:17:53 +0300 (EEST) From: Matti Aarnio MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-Id: <19990525221804Z92392-10847+102@mea.tmt.tele.fi> Sender: owner-linux-mm@kvack.org To: Rik van Riel Cc: alan@lxorguk.ukuu.org.uk, ak@muc.de, ebiederm+eric@ccr.net, linux-kernel@vger.rutgers.edu, linux-mm@kvack.org List-ID: Rik van Riel wrote: ... > This sounds suspiciously like the 'larger-blocks-for-larger-FSes' > tactic other systems have been using to hide the bad scalability > of their algorithms. ... (read-ahead comments cut away) ... I have this following table about EXT2 (and UFS, and SysVfs, and..) filesystem maximum supported file size. These limits stem from block addressability limitations in the classical tripply-indirection schemes: Block Size File Size 512 2 GB + epsilon 1k 16 GB + epsilon 2k 128 GB + epsilon 4k 1024 GB + epsilon 8k 8192 GB + epsilon ( not without PAGE_SIZE >= 8 kB ) And of course any single partition filesystem in Linux (all of the 'local devices' filesystems right now) can't exceed 4G blocks of 512 bytes which limit is at the block device layer. (This gives maximum physical filesystem size of 2 TB for EXT2.) So, in my opinnion any triply-indirected filesystem is at the end of its life when it comes to truly massive datasets. The EXT2FS family will soon get new ways to extend its life by having alternate block addressing structure to that of the classical triply- indirection scheme it now uses. (Ted Ts'o is working at it.) > Rik -- Open Source: you deserve to be in control of your data. /Matti Aarnio -- To unsubscribe, send a message with 'unsubscribe linux-mm my@address' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://humbolt.geo.uu.nl/Linux-MM/