From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ric Wheeler Subject: Re: mpt2sas logged messages Date: Tue, 18 Aug 2009 13:44:34 -0400 Message-ID: <4A8AE882.7050105@redhat.com> References: <4A8AAA26.9090706@redhat.com> <20090818132518.GA4418@kroah.com> <4A8AB3DC.4060805@redhat.com> <20090818145710.GA6064@kroah.com> <4A8ACE7C.5080501@redhat.com> <1250611768.6971.6.camel@mulgrave.site> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mx2.redhat.com ([66.187.237.31]:44311 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752561AbZHRRmt (ORCPT ); Tue, 18 Aug 2009 13:42:49 -0400 In-Reply-To: <1250611768.6971.6.camel@mulgrave.site> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: Greg KH , linux-scsi@vger.kernel.org, kay.sievers@vrfy.org, Tom Coughlan On 08/18/2009 12:09 PM, James Bottomley wrote: > On Tue, 2009-08-18 at 11:53 -0400, Ric Wheeler wrote: >> On 08/18/2009 10:57 AM, Greg KH wrote: >>> On Tue, Aug 18, 2009 at 09:59:56AM -0400, Ric Wheeler wrote: >>> >>>> On 08/18/2009 09:25 AM, Greg KH wrote: >>>> >>>>> On Tue, Aug 18, 2009 at 09:18:30AM -0400, Ric Wheeler wrote: >>>>> >>>>>> We have a new toy to test very large& slow storage with built up from 5 >>>>>> SAS expansion shelves (Promise Vtrak J-Class) with 60 S-ATA drives and >>>>>> 16 SAS drives (the S-ATA drives each have a Promise Vtrak S-ATA MUX >>>>>> adapter daughter card in the disk sled). >>>>>> >>>>>> The basic idea is to build a cheap& slow test bed for file& storage >>>>>> system scalability. Collectively, we have about 120TB (raw) of capacity >>>>>> to play with in one server. >>>>>> >>>>>> As we work through various issues, a couple of oddities popped out. >>>>>> >>>>>> The first is that udev grumbles during boot about "file name too long" >>>>>> like the following: >>>>>> >>>>>> Aug 17 06:49:58 megadeth udevd-event[20447]: unable to create db file >>>>>> '/dev/.udev/db/\x2fdevices\x2fpci0000:00\x2f0000:00:04.0\x2f0000:17:00.0\x2f0000:18:0a.0\x2f0000:1f:00.0\x2fhost11\x2fport-11:0\x2fexpander-11:0\x2fport-11:0:0\x2fexpander-11:1\x2fport-11:1:0\x2fexpander-11:2\x2fport-11:2:17\x2fexpander-11:3\x2fport-11:3:1\x2fend_device-11:3:1\x2fbsg\x2fend_device-11:3:1': >>>>>> File name too long >>>>>> >>>>> Odd, what is the sysfs tree for this device? You have expanders >>>>> attached to ports attached to expanders? How deep can you go? >>>>> >>>>> thanks, >>>>> >>>>> greg k-h >>>>> >>>> There are two dual-port SAS HBA's in the server that plug into the first of the >>>> 5 SAS expansion shelves. Each shelf has two internal SAS loops and is daisy >>>> chained to the next shelf.... This test is running with just the first 4 >>>> shelves active (although that fifth shelf is plugged in, just not used/active). >>>> >>>> Each of the 60 S-ATA disks sits behind a MUX card which lets it appear on both >>>> loops. >>>> >>>> We could break up the shelves into two independent sets of devices which would >>>> limit the tree depth. >>>> >>>> How can I get you the sysfs tree information in a useful way? >>>> >>> 'tree /sys/devices/' >>> or >>> 'find /sys/devices/' >>> would be good. >>> >>> thanks, >>> >>> greg k-h >>> >> >> Attached is the bzipped output from - the uncompressed output is quite >> large. Note that this same server has CCIS controllers and fibre HBA's >> as well, > > It's perfectly legal the way you have it, but I will say you have an > inefficient configuration. The way a configuration like this is > supposed to look is that there should be a fanout expander at the top > going to the expander in each tray, for a routing depth of two for every > device. > > The way you've got it: expander daisy chained off the next expander > gives an unnecessary routing delay to the disks furthest away in the > chain. > > James I understand that this configuration is not optimal, but from what I saw with some commercial arrays, this is not an uncommon config (up to 4 shelves) when going for capacity over performance. Do you have a particular SAS fanout expander in mind? I suppose that we could always add more hba's as well which would have other benefits... Thanks! Ric