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On Fri, 2008-03-07 at 11:40 -0500, Ben Holland wrote: > Ahhh I am not sure now, it very well could have been psudo raid but > there was a built in raid controller that once the bios booted up you > could configure your settings. It is quite possible that this was in > fact done with bios driven stuff which I don't think I would ever wish > to use. I find bios RAID to be okay for RAID-1 sometimes, but I don't really trust it beyond that, and I believe with some bios RAID setups, the only way to do any sort of recovery/rebuild is via their tools that load in the bios. I definitely prefer something where I can hot-swap drives and have utilities that run within the operating system while booted to prod the array. > I do know though that every time I've had a SCSI controller it's had > RAID built in to the hardware Dell boxes with on-board SCSI controllers tend to ship just a plain old SCSI controller by default. Getting RAID functionality requires adding a RAID personality card, which enhances the on-board controller with RAID functionality, or a replacement/add-on controller. > SATA most of the comps didn't but they were also really low end and > the newer ones said they had some form of RAID Just about guaranteed to be crap bios RAID. > the few that had >4 drives generally came with raid 5, in this day and > age I wouldn't buy a computer that could take >=4 drives without > getting hardware raid 5 built in to hardware, but that may mean i'm a > picky bastard, which I freely admit to being. Not as picky as I am. :) Any hardware RAID solution I bought today would need to support RAID6. I've been the unfortunate recipient of a double-disk failure a time or two, in both the form of two disks in an array hitting errors and dropping out of the array, and in the form of a second disk failing while rebuilding the array with a hot spare or replacement. > Just a quick question, how do you know if what you are getting has > real raid vs psudo raid if they both look the same? Not sure exactly, but I don't think I've actually seen anything but a Dell server with an add-on personality card that could actually do hardware RAID with an on-board SATA controller. I suppose one way to know is to boot a modern Linux live CD and see what controllers it sees, and what drives it sees attached to those controllers. If its true hardware RAID, Linux will see a single "drive" attached to the controller, like so: scsi 4:1:0:0: Direct-Access MegaRAID LD 0 RAID5 915G 713N PQ: 0 ANSI: 2 sd 4:1:0:0: [sdc] 1875400704 512-byte hardware sectors (960205 MB) With bios RAID, Linux will actually see all the individual drives connected to the controller, it just knows to handle them as a single drive via the dmraid layer if the drives have appropriate bios RAID metadata scribbled on them. (dmraid == device mapper raid == bios pseudo-raid support, mdraid is linux kernel software raid). -- Jarod Wilson [hidden email] -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. _______________________________________________ Discuss mailing list [hidden email] http://lists.blu.org/mailman/listinfo/discuss
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