Date: Fri, 30 Jun 2000 18:40:22 +1000 From: Greg Lehey <grog@lemis.com> To: Rasmus Skaarup <rasmus@gal.dk> Cc: Soren Schmidt <sos@freebsd.dk>, Jaye Mathisen <mrcpu@internetcds.com>, hackers@FreeBSD.ORG Subject: Re: vinum and superblocks. Message-ID: <20000630184022.G7687@sydney.worldwide.lemis.com> In-Reply-To: <Pine.BSF.4.21.0006300910360.37775-100000@skaarup.org> References: <200006300704.JAA85601@freebsd.dk> <Pine.BSF.4.21.0006300910360.37775-100000@skaarup.org>
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On Friday, 30 June 2000 at 9:16:33 +0200, Rasmus Skaarup wrote: > On Fri, 30 Jun 2000, Soren Schmidt wrote: > >> It seems Jaye Mathisen wrote: >>> >>> I have 8 75GB IBM drives striped in a big raid 0 for monkeying with. >>> >>> newfs -i 131072 -v /dev/vinum/bighonkindisk seems to very nicely put all >>> the data that newfs write out on to the first disk... It least, only the >>> first disk gets any io, accoring to systat and iostat. >> >> You need to adjust your stripe size so that the superblocks etc are >> not all put on the same disk, ie some odd stripe size is often best >> to distribute those to hopefully all disks... > > By 'odd', you mean small, Søren? If this is the case, be careful not to > make the size too small, which will degrade the perfomance because of the Of the? But yes, you don't want stripes of less than about 256 kB. > Jaye, are you sure you doing a large (preferrebly at least one > GB) sequential read or write from/to your disks? If you are only doing > small random I/O, this could result in only one disk getting hit. > > But it does sound strange that when making the filsystem, only the > first disk gets initialized.. Are you positively sure about this? It sounds right to me. It seems I can't find the text I had intended to put in the man page; I'll follow up with this some time soon. But indeed, the access pattern for newfs will write only to the first subdisk if the stripe size is, say, 512 kB. I'm currently recommending odd stripe sizes like 273 kB; calculate something which will put superblocks 32 MB apart onto consecutive subdisks. Greg -- Finger grog@lemis.com for PGP public key See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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