Date: Wed, 13 Jun 2007 11:06:56 +0200 From: Filip Palian <filip.palian@hyperion.pl> To: Tom Judge <tom@tomjudge.com> Cc: freebsd-performance@freebsd.org Subject: Re: Dell/Perc5 raid/MPT SAS Integrated Raid Write Performance Message-ID: <466FB3B0.2080600@hyperion.pl> In-Reply-To: <466937BC.10703@tomjudge.com> References: <46692AC6.30700@hyperion.pl> <466937BC.10703@tomjudge.com>
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Tom Judge pisze: > Filip Palian wrote: >> Hi folks, >> >> I've also encountered problems with write performnce on PE860, below are >> some details. >> >> > > I believe that a fix for this went into RELENG_6 this week. > Scott Long MFC'd the following fix at 2007-06-05 21:32:57. > > Tom > Great thing that sombody cares. > Commit Message: > > scottl 2007-06-03 23:13:05 UTC > > FreeBSD src repository > > Modified files: > sys/dev/mpt mpt.c mpt.h mpt_cam.c > Log: > mpt.c: > mpt.h: > Add support for reading extended configuration pages. > mpt_cam.c: > Do a top level topology scan on the SAS controller. If any > SATA device are discovered in this scan, send a passthrough FIS to set > the write cache. This is controllable through the following tunable at > boot: > hw.mpt.enable_sata_wc: > -1 = Do not configure, use the controller default > 0 = Disable the write cache > 1 = Enable the write cache > > The default is -1. This tunable is just a hack and may be > deprecated in the future. > Unfortunatly I couldn't use this fix because disk performance is crucial for me and i could not depend on the "hack" which may be "deprecated in the future". > Turning on the write cache alleviates the write performance problems > with SATA that many people have observed. It is not recommend for those > who value data reliability! I cannot stress this strongly enough. > However, it is useful in certain circumstances, and it brings the > performence in line with what a generic SATA controller running under > the FreeBSD ATA driver provides (and the ATA driver has had the WC > enabled by default for years). > Just for curiosity I've tried to run FreeBSD 6.2 in Xen and KVM with Gentoo as a host system. Under Xen nothing could be done because of "BTX halted" error with the same values as described in the bug "http://lists.freebsd.org/pipermail/freebsd-bugs/2006-November/020906.html" (in my example it was an IDE cdrom). But happily KVM did the work. I've intsalled FreeBSD and run blogbench and guess what... The results were: Final score for writes: 84 Final score for reads : 13636 Summing up, I'll wait for 7.0 release and then I'll put my hands on it. Regards, Filip Palian
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