Date: Thu, 28 Feb 2013 14:12:08 -0000 From: "Steven Hartland" <killing@multiplay.co.uk> To: "rihad" <rihad@mail.ru>, "John Baldwin" <jhb@freebsd.org> Cc: freebsd-stable@freebsd.org, vince@unsane.co.uk Subject: Re: mfi timeouts Message-ID: <5FB0404788D04ABC814D11A67B536304@multiplay.co.uk> References: <512CFF90.8080806@mail.ru> <201302261548.56253.jhb@freebsd.org> <512DA073.9090908@mail.ru> <201302271159.13424.jhb@freebsd.org> <512EECD4.5080600@mail.ru>
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----- Original Message ----- From: "rihad" <rihad@mail.ru> To: "John Baldwin" <jhb@freebsd.org> Cc: <freebsd-stable@freebsd.org>; <vince@unsane.co.uk> Sent: Thursday, February 28, 2013 5:36 AM Subject: Re: mfi timeouts > On 02/27/2013 08:59 PM, John Baldwin wrote: >> On Wednesday, February 27, 2013 12:58:11 am rihad wrote: >>> Now about this part taken from here >>> http://lists.freebsd.org/pipermail/freebsd-scsi/2011-March/004839.html >>> > By issuing a dummy read operation (thus forcing a flush of data >>> buffers), this issue is largely averted. >>> >>> Does this mean that battery-backed cache (BBU) is effectively rendered >>> useless, as all write operations are forced on to the disk platters on >>> every interrupt? >> No, this is a very different level. This is forcing pending PCI DMA >> transactions on the PCI bus to flush by doing a read, not forcing I/O >> buffers to be flushed to disk. >> > Thanks for clarifying. > > After applying the "dummy read" patch mfi timeouts don't appear in dmesg > output any more, but i/o stalls still occurred 2-3 times during periods > of high activity, for no more than 10-20 seconds. I guess the only way > to fix that is to choose another hardware RAID implementation, or try > Steven Hartland's patch? Does 8.3 or 9.1 include more fixes in this > area, is upgrading recommended? 8.3 and 9.1 are way behind head and I'm not aware of any significant changes to them which may help you there rihad. I would recommend using mfi from HEAD even if you stick with 8.3 or 9.1 as a base, it shouldn't require much work to back port, just avoid the busdma changes. Regards Steve ================================================ This e.mail is private and confidential between Multiplay (UK) Ltd. and the person or entity to whom it is addressed. In the event of misdirection, the recipient is prohibited from using, copying, printing or otherwise disseminating it or any information contained in it. In the event of misdirection, illegible or incomplete transmission please telephone +44 845 868 1337 or return the E.mail to postmaster@multiplay.co.uk.
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