Date: Thu, 22 Oct 1998 23:09:33 -0600 From: "Justin T. Gibbs" <gibbs@plutotech.com> To: Don Lewis <Don.Lewis@tsc.tdk.com> Cc: "Justin T. Gibbs" <gibbs@plutotech.com>, freebsd-fs@FreeBSD.ORG, freebsd-scsi@FreeBSD.ORG Subject: Re: filesystem safety and SCSI disk write caching Message-ID: <199810230516.XAA29829@pluto.plutotech.com> In-Reply-To: Your message of "Thu, 22 Oct 1998 22:10:03 PDT." <199810230510.WAA19810@salsa.gv.tsc.tdk.com>
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>} There has been quite a bit of debate on how UAs should be handled. The >} original CAM driver was *very* conservative and returned all pending >} I/O with EIO, marked the pack invalid, and refused to take any I/O unless >} the device cycled through final close. This ensures that if the device >} or pack is replaced that you don't spam different media or even if the >} media is the same, make the problem worse by attempting to continue after >} some transactions were irrevocably lost. This was considered too >} disruptive and since a permanent solution could not be developed for >} 3.0R, the UA code was disabled. The correct solution likely requires >} better communication to the FS or user layer so that pack validation >} of some sort can occur. > >If write caching is disabled and if it is possible to verify that the >media is the same, it should be safe to retry all the lost I/O >transactions. You can't retry the transactions without first determining that the media is the same as before. We can't do that right now without manual intervention which shouldn't be the case. -- Justin To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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