Date: Sat, 17 Sep 2011 14:58:16 -0500 (CDT) From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us> To: Jason Usher <jusher71@yahoo.com> Cc: "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org> Subject: Re: ZFS obn FreeBSD hardware model for 48 or 96 sata3 paths... Message-ID: <alpine.GSO.2.01.1109171451500.1973@freddy.simplesystems.org> In-Reply-To: <1316222526.31565.YahooMailNeo@web121205.mail.ne1.yahoo.com> References: <1316222526.31565.YahooMailNeo@web121205.mail.ne1.yahoo.com>
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This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. ---559023410-649254455-1316289496=:1973 Content-Type: TEXT/PLAIN; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8BIT On Fri, 16 Sep 2011, Jason Usher wrote: > > So I will boot of a pair of mirrored SSDs formatted UFS2 - easy. > But I would also like to spec and use a ZIL+L2ARC and am not sure > where to go ... the system will be VERY write-biased and use a LOT > of inodes - so lots of scanning of large dirs with lots of inodes > and writing data. Something like 400 million inodes on a filesystem > with an average file size of 150 KB. 150KB is a relatively small file size given that the default zfs blocksize is 128KB. With so many files you should definitely max out RAM first before using SSDs as a l2arc. It is important to recognize that the ARC cache is not populated until data has been read. The cache does not help unless the data has been accessed several times. You will want to make sure that all metada and directories are cached in RAM. Depending on how the files are used/accessed you might even want to intentionally disable caching of file data. Are the writes expected to be synchronous writes, or are they asynchronous? Are the writes expected to be primarily sequential (e.g. whole file), or is data accessed/updated in place? Bob -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ ---559023410-649254455-1316289496=:1973--
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