Date: Wed, 10 May 2006 18:30:33 +0200 From: Andrea Venturoli <ml@netfence.it> To: Atom Powers <atom.powers@gmail.com>, freebsd-questions@freebsd.org Subject: Re: OT: Torn between SCSI and SATA for RAID Message-ID: <44621529.7050804@netfence.it> In-Reply-To: <df9ac37c0605100912s46bffe8an7c1212c4ca0330e5@mail.gmail.com> References: <1147255200.4461b9a0a5e71@196.22.132.16> <df9ac37c0605100912s46bffe8an7c1212c4ca0330e5@mail.gmail.com>
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Atom Powers wrote: >> >> Another thing that I read that I'm not completely sure about. Some of >> the Adaptec SCSI Cards advertises a max of 30 devices - some even >> more. Excuse the ignorance, but does the SCSI Bus not allow for a max >> of 8 devices? Do these cards then feature multiple buses to connect >> the cables to? > I am not that familiar with SCSI protocols, but I imagine the > Ultra-Wide SCSI bus can probably address 32 devices ( 31 drives + the > controller ). Old 8-bit SCSI allow for 8 devices. For HD today you'll want Wide (16-bit) SCSI, which allows for 16 devices (15 drives + controller). There is no 32-bit SCSI, AFAIK. The Adaptec cards you mention do have two busses (basically they are two controllers on one chip and are as such seen by the OS). >> Can SATA RAID Controllers be 'linked'. >> ... can I extend a array across multiple controllers... > I imagine you would probably have to use software raid at that point. Yes and true. > And even if you would use two controllers togeather (SLI for RAID?) > you would be limited by the PCI bus. You might want a motherboard with multiple PCI buses and carefully choose the RAID scheme vs. HD distribution. If you need so many drives, however, you might well be better off with an hardware solution. > Probably with softawre RAID. With software RAID you can even mix drive > types, like SATA, PATA, SCSI, USB, etc. But it's much slower. I wouldn't want to do that... I've always heard you should get identical drives to build an array. Of course you might have different arrays on the same machine... bye av.
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