Date: Mon, 9 Dec 2013 05:50:35 +0000 From: "Desai, Kashyap" <Kashyap.Desai@lsi.com> To: Doug Ambrisko <ambrisko@cisco.com> Cc: "scottl@netflix.com" <scottl@netflix.com>, "Radford, Adam" <Adam.Radford@lsi.com>, "Kenneth D. Merry" <ken@kdm.org>, "sean_bruno@yahoo.com" <sean_bruno@yahoo.com>, "Mankani, Krishnaraddi" <Krishnaraddi.Mankani@lsi.com>, "dwhite@ixsystems.com" <dwhite@ixsystems.com>, "Maloy, Joe" <Joe.Maloy@lsi.com>, "jpaetzel@freebsd.org" <jpaetzel@freebsd.org>, "freebsd-scsi@freebsd.org" <freebsd-scsi@freebsd.org>, "McConnell, Stephen" <Stephen.McConnell@lsi.com> Subject: RE: LSI - MR-Fusion controller driver <mrsas> patch and man page Message-ID: <4ebf0c915b784464827c30858a42d54f@BN1PR07MB247.namprd07.prod.outlook.com> In-Reply-To: <20131206162211.GB14280@cisco.com> References: <08ba2a262fba45f687cdd3225f325110@BN1PR07MB247.namprd07.prod.outlook.com> <20131206162211.GB14280@cisco.com>
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> -----Original Message----- > From: Doug Ambrisko [mailto:ambrisko@cisco.com] > Sent: Friday, December 06, 2013 9:52 PM > To: Desai, Kashyap > Cc: freebsd-scsi@freebsd.org; scottl@netflix.com; sean_bruno@yahoo.com; > dwhite@ixsystems.com; jpaetzel@freebsd.org; Maloy, Joe; Mankani, > Krishnaraddi; McConnell, Stephen; Saxena, Sumit; Radford, Adam; Kenneth > D. Merry > Subject: Re: LSI - MR-Fusion controller driver <mrsas> patch and man page >=20 > Sounds like good progress. I'll need to play with it a bit. One questio= n I have > with fast path, is how does LSI determine if they should use that method > versus the RAID firmware? The problem I've seen with fast path is that i= t > skips the NVRAM cache which is a huge performance boost for us. Is there= a > sysctl to control it?=20 Fast Path will not be enabled for Cached VDs. Driver choose Fast Path provi= ded information from firmware. You can find out those bits (fpCapable) in Raid Map. > I could probably read through the code to figure it out but > thought it would be good to get an idea of how LSI plans to use it since = you > guys are the experts on this feature. I understand from Adam that LSI us= es > this to increase the IOPS. I can see it potentially used if an SSD is in= the > system so then LD or PD access could be improved to that type of device. = In > past experience fast path was slower and created a bunch of SCSI sense > errors reported by the RAID firmware. That is one reason why I removed > support of fastpath in mfi. I also didn't want to introduce potential bu= gs if > the RAID firmware and driver got out of sync. due to bugs. Recently we > found with SW RAID that trying to load balance IOs across drives can defe= at > read ahead caches of disks. LSI have never heard anything like above in <megaraid_sas> linux Driver or = any other OS driver for MR controllers. If there is really such a case, we can correct it or provide user option to= bypass load balancing, but as I mentioned, we have never hear anything lik= e that from customer. Thanks, Kashyap >=20 > Thanks, >=20 > Doug A. >=20 > On Fri, Dec 06, 2013 at 02:37:21PM +0000, Desai, Kashyap wrote: > | Hi, > | > | Please consider attached patch for FreeBSD upstream check-in. > | > | Please find attached patch for <mrsas> driver for LSI's MegaRaid > Controllers. This driver supports Thunderbolt onwards Device IDs of MR > controllers. > | Currently it supports 0x005B and 0x005D Device IDs. > | > | NOTE : This driver will not eliminate or by pass any functionality of <= mfi> > driver which already support above to Device IDs to keep existing user > experience unchanged. > | > | <mfi> Driver will be always given priority over <mrsas> driver and > | only if customer/user wants to use/migrate from <mfi> to <mrsas>, it > | will hook up into kernel via device.hint rules. (Attached is mrsas man > | page for more info.) > | > | LSI will continue to update <mrsas> driver in future in timely bases. > | We have another set of patch in pipeline to be submitted for <mrsas>, > | but need first go ahead for attached patch and later we will continue > | to keep <mrsas> up-to-date (In sync with LSI released driver which is > | available at lsi's external site) > | > | Apply patch with "patch -p0 < patchname.patch" from head directory. > | > | -- Few notes for user-- > | LSI recommends using fusion_force bit In hint settings at start of the = day, if > they want to use <mrsas>. ( <mfi> will be a default choice for MR-Fusion > HBA), if will be changed only with fusion_force hint settings. (See mrsas= man > page) Changing any default behavior is well tested for most of the condit= ion. > | Switching from <mfi> to <mrsas> for MR-Fusion options is designed to > allow user as one time choice, though multiple time switch from <mfi> to > <mrsas> is possible, it is not recommended. So, user needs to decide from > start of the day, which driver they want to use for MR-Fusion card. > | > | -- Implementation details -- > | To support this feature, we have modify <mfi> code to change default > return type from probe. Currently <mfi> driver return > "BUS_PROBE_DEFAULT". <mfi> driver has been be changed to return > "BUS_PROBE_LOW_PRIORITY" if fusion_force hint from device.hints is set. > | Please notice, above mentioned implementation in <mfi> driver is only > applicable in case of MR-Fusion controller detection. For any other > controllers, supported by <mfi> driver, the behavior of probe return will > remain same as before. > | > | > | -- High level feature list of <mrsas> -- 1. Supports Fast Path feature > | of LSI controllers. > | 2. Supports 4K sector Drives. > | 3. CAM layer based interface. All VDs will be attached to CAM layer > | (Expected storage will be visible in "camcontroll") 4. Complete > | support of Online Controller Reset. (OCR) 5. OCR on Fimrware fault and= IO > timeout case. > | 6. Work well with <storcli> management application which is generic > application provided by LSI for all other Operating system. > | 7. Supporst DIF enabled VDs (Same support as provided in Linux and > | other OSes in FreeBSD) 8. Fast Path Load balance support. > | > | - In summary, this driver is in part with Linux based MR drivers and > | all other features will be available to <mrsas> as planned activity > | from LSI > | > | This code is well tested by LSI Q/A team on 32 bit and 64 bit FreeBSD > Released OSes. > | > | > | Thanks, Kashyap > | >=20 >=20 >=20
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