Date: Wed, 5 Feb 2014 03:08:34 -0500 From: Rich <rincebrain@gmail.com> To: Daniel Kalchev <daniel@digsys.bg> Cc: freebsd-fs <freebsd-fs@freebsd.org> Subject: Re: practical maximum number of drives Message-ID: <CAOeNLuqhT1y7rzA2=80jzXByrYy0cbCTaFv-5=X1KOnkFtRN8Q@mail.gmail.com> In-Reply-To: <52F1DEBC.9020304@digsys.bg> References: <52F1BDA4.6090504@physics.umn.edu> <7D20F45E-24BC-4595-833E-4276B4CDC2E3@gmail.com> <52F1DEBC.9020304@digsys.bg>
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The SAS2008 has a limit of 112 drives? http://www.lsi.com/downloads/Public/SAS%20ICs/LSISAS2008/SCG_LSISAS2008_PB_043009.pdf claims "up to 3000 devices." SAS2008 is a PCIe gen 2 x8 chip. I suspect the bottleneck order would go SAS expander then SAS2008 then PCIe. - Rich On Wed, Feb 5, 2014 at 1:48 AM, Daniel Kalchev <daniel@digsys.bg> wrote: > I also wonder how you managed to go over the LSI2008's limit of 112 > drives... > > > On 05.02.14 07:36, aurfalien wrote: >> >> Hi Graham, >> >> When you say behaved better with 1 HBA, what were the issues that made you >> go that route? >> >> Also, curious that you have that many drives on 1 PCI card, is it PCI 3 >> etc... and is saturation an issue? >> >> - aurf >> >> On Feb 4, 2014, at 8:27 PM, Graham Allan <allan@physics.umn.edu> wrote: >> >>> This may well be a question with no real answer but since we're speccing >>> out a new ZFS-based storage system, I've been asked what the maximum number >>> of drives it can support would be (for a hypothetical expansion option). >>> While there are some obvious limits such as SAS addressing, I assume there >>> must be more fundamental ones in the kernel or drivers, and the practical >>> limits will be very different from the hypothetical ones. >>> >>> So far the largest system we've built is using three 45-drive chassis on >>> one SAS2008 (mps) controller, so 135 drives total. Over many months of >>> running we had several drives fail and be replaced, and eventually the OS >>> (9.1) failed to assign new da devices. It was time to patch the system and >>> reboot anyway, which solved it, but we did wonder if we were running into >>> some kind of limit around 150 drives - though I don't see why. >>> >>> Interestingly we initially built this system with each drive chassis on >>> its own SAS2008 HBA, but it ultimately behaved better daisy-chained with >>> only one. I think I saw a hint somewhere this could be to do with interrupt >>> sharing... >>> >>> Thanks for any insights, >>> >>> Graham >>> _______________________________________________ >>> freebsd-fs@freebsd.org mailing list >>> http://lists.freebsd.org/mailman/listinfo/freebsd-fs >>> To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" >> >> _______________________________________________ >> freebsd-fs@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-fs >> To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" > > > > _______________________________________________ > freebsd-fs@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org"
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