Software RAID-1 on FreeBSD 5.4

Ted Mittelstaedt tedm at
Thu Jun 30 09:02:22 GMT 2005

One last comment for you on software mirroring,

  While I am not trying to disparage the various efforts, software
mirroring provides limited redundancy unless the hard drives
are on separate busses.

  If you do the common thing of putting 2 IDE drives as the master and
slave on the primary IDE controller, than all it takes is a buss error
on the IDE bus and you have scrambled the data on both hard drives.

  The same problem exists if you setup a ccd or vinum or gmirror
or whatever on a SCSI controller where the disks are all on the same
SCSI bus.

  The same problem also exists on SATA controllers, and on cheaper
hardware RAID cards where the disks are on a single IDE bus.

  This is why hardware RAID controllers are quite often better as
the better ones contain multiple interfaces.


>-----Original Message-----
>From: owner-freebsd-questions at
>[mailto:owner-freebsd-questions at]On Behalf Of ptitoliv
>Sent: Wednesday, June 29, 2005 12:56 PM
>To: freebsd-questions at
>Subject: Re: Software RAID-1 on FreeBSD 5.4
>Hello again,
>Thank you for all your answers ! I am going to look at gmirror and ccd.
>But I have a last question. My disks are differents. One is a Maxtor
>detected with a 111 GB capacity and the other is a Seagate detected with
>a 114 GB capacity. Will I have problems trying to use RAID with this
>configuration ?
>Best regards,
>freebsd-questions at mailing list
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