Date: Mon, 13 Jul 1998 18:43:01 -0500 From: Raul Zighelboim <rzig@verio.net> To: "'freebsd-scsi@freebsd.org'" <freebsd-scsi@FreeBSD.ORG> Subject: FW: Another question about DPT Message-ID: <A03CD00C69B1D01195AB00A024ECEB16A6F410@kaori.INTERNAL>
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Here we go! > -----Original Message----- > From: Simon Shapiro [SMTP:shimon@simon-shapiro.org] > Sent: Monday, July 13, 1998 7:42 PM > To: Raul Zighelboim > Subject: RE: Another question about DPT > > > On 12-Jul-98 Raul Zighelboim wrote: > > > > Hello Smon; I ran into this extension of the DPT controller: > > http://www.dpt.com/dpt-dbus.htm > > Will FreeBSD support this configuration with 2 independet servers > > sharing the spool array ? > > Sorry for the delay... > > The dual-bus simply allows you to split the bus of a disk shelf/bay > into > two electrically independant bays. I use this option frequently to > increase perfromace; The true capacity of a SCSI bus (for random > access, > RDBMS type work) is about 4 drives. This option also increases > availability as there are two busses instead of one. > > The other part of your question is different. To hook up a SCSI bus > to two > HBAs require careful consideration of bus termination (DPT can supply > you > with an adapter which will allow you to split the bus), bus mastering, > etc. > The hardware is all there. Another consideration, DPT-specific, is > which > HBA ``owns'' the RAID arrays at any given moment. This is > particularly > critical in the case of RAID-5 and RAID-1, which need parity (or > mirrror) > writes, etc. Things get messy quickly when you consider hot standby, > automatic rebuild, etc. > > Much of the core work for this was already done, but overall, the > solution > is not complete yet. > > I have suspended this work until we complete moving the DPT driver to > CAM. > It makes little sense to do it twice. > > If you agree, please forward this reply to freebsd-scsi@freebsd.org. > It > may be of interest to others. > > > > Sincerely Yours, > > Simon Shapiro > Shimon@Simon-Shapiro.ORG > 770.265.7340 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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