Messages in this thread | | | Date | Sat, 14 Sep 1996 05:20:35 +0200 (MET DST) | From | Michael Neuffer <> | Subject | Re: Disk Mirroring |
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On 12 Sep 1996, Mike Bristow wrote: > >Can anyone tell me if there is a way of mirroring disks in Linux? We use > >this approach at work to give our system online redundance so if a disk > >starts to go bad, we break the mirror and take the offending disk/partitions > >off line until the repair/replacement is done. Since all data is > >duplicated on the mirror device, the user has no idea that a disk failure > >has occured. > > > You're after RAID support. Doesn't exist (yet). Very Clever People > are working on it...
Not quite true, hardware controller based RAID has been in use under Linux for over 3 years now. Since then, the driver for the DPTs (EATA-DMA) has been available.
> For the cuurent state of play, look into md. > > As I understand it, this is never as good as a special RAID controller. > <simplifcation> > This is a very clever box, which pretends to be a SCSI (or whatever) HDD > while actually containing 9 (or whatever) real SCSI HDD's. As far as Linux > is concerned, it's just got a SCSI HDD, and doesn't care any more. > </simplifcation>
Yes, it is a little too much simplified (you're mixing external SCSI--SCSI RAID subsystems with internal SCSI RAID controllers here) but otherwise the idea is correct.
> These are normally better than a software solution, because you can do > things like take out a broken HDD, and replace it, while the system > is online.
True.
> They are, howvere, expensive....
But those who really need the IO performance and/or security are willing to pay for it, since they know it is worth it.
Mike
Michael Neuffer i-Connect.Net, a Division of iConnect Corp. mike@i-Connect.Net 14355 SW Allen Blvd., Suite 140 503.677.2900 Beaverton, OR 97008 ====================================================================== "Maybe you should telephone the Internet and talk to their tech support people." (Reply from an AOL tech-support rep speaking to a customer complaining about e-mail that failed to go through.) (SOURCE: Internet World, February 1995, p. 18) ======================================================================
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