Date: Mon, 19 Sep 2011 12:11:42 -0700 (PDT) From: Jason Usher <jusher71@yahoo.com> To: freebsd-fs@freebsd.org Subject: Re: ZFS obn FreeBSD hardware model for 48 or 96 sata3 paths... Message-ID: <1316459502.23423.YahooMailClassic@web121212.mail.ne1.yahoo.com> In-Reply-To: <alpine.GSO.2.01.1109191403020.7097@freddy.simplesystems.org>
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--- On Mon, 9/19/11, Bob Friesenhahn <bfriesen@simple.dallas.tx.us> wrote: > > Hmmm... I understand this, but is there not any data > that might transfer from multiple magnetic disks, > simultaneously, at 6GB, that could periodically max out the > card bandwidth ? As in, all drives in a 12 drive array > perform an operation on their built-in cache simultaneously > ? > > The best way to deal with this is by careful zfs pool > design so that disks that can be expected to perform related > operations (e.g. in same vdev) are carefully split across > interface cards and I/O channels. This also helps with > reliability. Understood. But again, can't that all be dismissed completely by having a one drive / one path build ? And since that does not add extra cost per drive, or per card ... only per motherboard ... it seems an easy cost to swallow - even if it's a very edge case that it might ever be useful. Presuming I can *find* a 112+ lane mobo, I assume the cost would be at worst double ($800ish instead of $400ish) a mobo with fewer pcie lanes...
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