Date: Fri, 25 Dec 2009 12:30:57 -0500 From: Gary Palmer <gpalmer@freebsd.org> To: Alexander Motin <mav@FreeBSD.org> Cc: FreeBSD-Current <freebsd-current@freebsd.org>, freebsd-arch@freebsd.org Subject: Re: File system blocks alignment Message-ID: <20091225173057.GA75881@in-addr.com> In-Reply-To: <4B349ABF.2070800@FreeBSD.org> References: <4B349ABF.2070800@FreeBSD.org>
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On Fri, Dec 25, 2009 at 12:58:07PM +0200, Alexander Motin wrote: > Hi. > > Recently WD released first series of ATA disks with increased physical > sector size. It makes writes not matching with 4K blocks inefficient > there. So I propose to get back to the question of optimal FS block > alignment. This topic is also important for most of RAIDs having striped > nature, such as RAID0/3/5/... and flash drives with simple controller > (such as MMC/SD cards). This is also a critical issue on certain SAN system. NetApp, I suspect as a result of them layering a virtual LUN ontop of another filesystem (WAFL), is very sensitive to filesystem alignment on the LUN. If the I/Os to the LUN are not 4k aligned, performance suffers a serious hit. I'm not sure what other SAN vendors suffer similar alignment restrictions. Regards, Gary
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