Date: Wed, 13 Jun 2001 22:15:34 -0500 From: Dan Nelson <dnelson@emsphone.com> To: "mail_box_of_mine@yahoo.com" <mail_box_of_mine@yahoo.com> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: _? About SCSI request Message-ID: <20010613221534.A19081@dan.emsphone.com> In-Reply-To: <20010613175933.BB5F.MAIL_BOX_OF_MINE@yahoo.com> References: <20010613175933.BB5F.MAIL_BOX_OF_MINE@yahoo.com>
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In the last episode (Jun 13), mail_box_of_mine@yahoo.com said: > hi, > I have post this question in freebsd-questions@freebsd.org. But > no one answer me, so I have to ask freebsd-scsi@freebsd.org. Thanks in > advance. > > I have a question: If the OS (FreeBSD) submit two write request > to a SCSI driver, will the two request overlap? eg. > block = 0 size = 30 > block = 3 size = 50 > will this case happen? Only if the two writes were caused by a user doing I/O on a file opened with the O_FSYNC flag, or if the user called fsync() on the filehandle between two writes, or if the writes are on a filesystem mounted sync. Most of the time, userland write() calls are cached for a little while before being written to disk, so FreeBSD would end up writing one block, 53 units long to disk. > How about other OS? (Linux? Windows? ....) > How about IDE request? Same rules apply. Both Linux and windows have a write cache. -- Dan Nelson dnelson@emsphone.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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