Date: Mon, 14 Jul 2003 12:34:41 +0930 From: Greg 'groggy' Lehey <grog@FreeBSD.org> To: Marc Wiz <marc@wiz.com> Cc: freebsd-questions@freebsd.org Subject: Re: vinum and hot-swapping Message-ID: <20030714030441.GU94666@wantadilla.lemis.com> In-Reply-To: <20030714030137.GG50589@freshaire.wiz.com> References: <200307130245.h6D2j8HB000556@soth.ventu> <20030713191453.GF23909@dan.emsphone.com> <20030714003258.GP94666@wantadilla.lemis.com> <20030714015746.GE50589@freshaire.wiz.com> <20030714021914.GR94666@wantadilla.lemis.com> <20030714030137.GG50589@freshaire.wiz.com>
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--ZjLa2K+dB9SFbrgo Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Sunday, 13 July 2003 at 22:01:37 -0500, Marc Wiz wrote: > On Mon, Jul 14, 2003 at 11:49:14AM +0930, Greg 'groggy' Lehey wrote: >> On Sunday, 13 July 2003 at 20:57:46 -0500, Marc Wiz wrote: >>> On Mon, Jul 14, 2003 at 10:02:58AM +0930, Greg 'groggy' Lehey wrote: >>>>> I don't believe vinum can optimize full-stripe writes, though, since >>>>> FreeBSD can only do I/O in 64k max chunks, >>>> >>>> 128 kB. >>> >>> I thought physio was limited to 64 KB? The man page on dump states >>> this. Please correct me if I am wrong. >> >> Physio is limited to MAXPHYS, which you'll find defined in >> /usr/include/sys/param.h: >> >> #ifndef MAXPHYS >> #define MAXPHYS (128 * 1024) /* max raw I/O transfer size */ >> #endif > > That's nice to know. What prevents it from being increased beyond > 128K? There are a couple of things, I think, but I can't recall what. Individual controllers and host adaptors sometimes have quirks. >> I've taken a look at the dump code (yuk!), and it no longer places any >> limitation on the block size. I'll fix the man page. > > Thanks. I have tried increasing the block size but going past 64K > does not seem to help performance. I will have to check the dump > code to see if it is limiting itself to a max of 64K. Check the dump with iostat 1. I think that the CAM layer currently restricts all I/O to 60 kB. If that's the case, you'll probably find that 60 kB blocks will be faster than 64 (which will give you an average block size of 30). Greg -- When replying to this message, please copy the original recipients. If you don't, I may ignore the reply or reply to the original recipients. For more information, see http://www.lemis.com/questions.html See complete headers for address and phone numbers --ZjLa2K+dB9SFbrgo Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.0 (FreeBSD) iD8DBQE/Eh3JIubykFB6QiMRAvMjAKChk0AUnZTLzq4VZK/ilFC3V/Fr7wCgtDWs A1WSH30NaoobHZ89QvZkMKg= =QaZ0 -----END PGP SIGNATURE----- --ZjLa2K+dB9SFbrgo--
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