Date: Thu, 2 Nov 2000 13:35:10 -0800 (PST) From: Matt Dillon <dillon@earth.backplane.com> To: Alfred Perlstein <bright@wintelcom.net> Cc: Marius Bendiksen <mbendiks@eunet.no>, Randell Jesup <rjesup@wgate.com>, arch@FreeBSD.ORG Subject: Re: Like to commit my diskprep Message-ID: <200011022135.eA2LZA740940@earth.backplane.com> References: <200011021725.eA2HPeM38718@earth.backplane.com> <Pine.BSF.4.05.10011022216250.13255-100000@login-1.eunet.no> <20001102132140.W20567@fw.wintelcom.net>
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:* Marius Bendiksen <mbendiks@eunet.no> [001102 13:19] wrote:
:> > Not to mention the bytes/inode (-i) If you want fsck to go fast on a
:> > big filesystem, reducing the number of inodes helps a lot. I find myself
:> > using -i 32768 or -i 65536 or even higher numbers on partitions which
:> > hold big database files.
:>
:> FFS is woefully inadequate at handling databases, due to the block
:> indirection, but e.g. Oracle will allow you to run directly on top
:> of a device.
:
:Block indirection could be optimized by attempting to allocate
:indirect blocks in the same area as either the inode or datablocks
:that the indirect blocks address.
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.
Consider a 32 GB table file:
BlockSize Bytes required to store leaf indirect blocks for a
32GB file
--------------- -----
8K blocks size 16MB
32K block size 4MB
calculation: filesize / blocksize * 4 =
# of bytes worth of leaf indirect blocks
required to reference the file. (higher
level indirect blocks are inconsequential)
It becomes somewhat more of an issue for a terrabyte-sized database,
but still no biggy considering the memory you can get these days.
A raw device will still be better, but not by much.
-Matt
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