Date: Thu, 21 Sep 2000 13:48:49 +0200 (CEST) From: Marius Bendiksen <mbendiks@eunet.no> To: Stephen Byan <Stephen.Byan@quantum.com> Cc: fs@FreeBSD.ORG, sos@FreeBSD.ORG, "'freeBSD-scsi@freeBSD.org'" <freeBSD-scsi@FreeBSD.ORG> Subject: RE: disable write caching with softupdates? Message-ID: <Pine.BSF.4.05.10009211346460.38107-100000@login-1.eunet.no> In-Reply-To: <8133266FE373D11190CD00805FA768BF055BD1C9@shrcmsg1.tdh.qntm.com>
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> Wouldn't it be acceptable to mark the meta-data writes as non-cacheable > (i.e. write though to the media before signalling completion), and let the > remaining writes (user data writes) be cacheable? I think this would improve > the performance of the file system. Actually, performance-wise, you'd probably want to know the real geometry, given all the stuff FFS does to exploit it. > SCSI has supported this for years, in the form of the FUA bit in the CDB for > the write command. Somewhat similar behavior can be had in the newer flavors As I recall, and from what Eivind noted, this bit is routinely ignored in about 90% of all drives out there. > of ATA by issuing a "flush cache" command after each meta-data write, and > waiting until the flush command completes before signalling the completion > of the non-cacheable write. This has the potential for degrading performance even further. I think you would prefer to disable cache over this. Marius To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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