Date: Tue, 26 Aug 1997 19:58:46 -0700 From: David Greenman <dg@root.com> To: Simon Shapiro <Shimon@i-Connect.Net> Cc: current@FreeBSD.ORG Subject: Re: IDE vs SCSI was: flags 80ff works (like anybody doubted it) Message-ID: <199708270258.TAA19831@implode.root.com> In-Reply-To: Your message of "Tue, 26 Aug 1997 10:26:06 PDT." <XFMail.970826102606.Shimon@i-Connect.Net>
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> >Hi David Greenman; On 26-Aug-97 you wrote: >> >FreeBSD does ALL its file I/O in 4K blocks. Your test is really a test >> >of the kernel's ability to issue strategy calls quickly, at best. >> >> Huh? No it doesn't; what ever gave you that idea? >> >> -DG > >Which idea? The 4K? I enable a certain debugging level >(DPT_DEBUG_COMPLETION) in the DPT driver, lean back and enjoy the messages >fly by. I have not seen anything larger than 4K yet. > >In SCSI, random disk I/O, up to about 8K blocks, the amount of time it FreeBSD can read and write up to 64KB, depending on various factors including the contiguousness of the file, the sequentialness of the accesses, and other factors. Random reads/writes to a file will usually happen in blocksize chunks which are either 4KB or (more commonly) 8KB. -DG David Greenman Core-team/Principal Architect, The FreeBSD Project
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