question about prblem with raid 1 for freeBSD

Matthew Seaman matthew at
Fri Jun 22 10:28:12 UTC 2012

On 22/06/2012 10:11, dude golden wrote:
> 1x Quad-Core i5-2500 3.3GHz, 6M Cache
> 16GB DDR3
> 2x 500GB SATAII

> then ask from my COLOCATION to install FreeBSD 8.2 or 8.3 with RAID
> 1, after many times of fail in installation from colocation they said
> that we have problem with RAID 1.we suggest them to play with
> different kind of RAID like RAID 5 and they said as our requested
> server only have 2 HDD, its not possible to set up RAID 5.

Correct.  RAID5 requires at least 3 drives. The only way to have
resilience against disk failure with just two drives is to use RAID1

How exactly are your colleagues attempting to set up RAID1.  There are
several different ways of doing it, but these are the most popular:

   * Using the built-in ATAPI RAID provided by many motherboards

   * gmirror

   * ZFS

ATAPI RAID is perhaps the least effective, and may require downtime in
order to rebuild the system after a disk failure.  I suspect this is
what is causing your colleagues problems.

For setting up a gmirror RAID see this article:

(That will work fine with 8.2 or older and the old sysinstall; needs to
be adapted if using the new bsdinstall with gpart)

For setting up a ZFS mirror, see:

or I wrote a similar piece assuming use of bsdinstall:

Both of the gmirror or ZFS procedures involve going beyond what the
installer provides and doing at least part of the work from the command
line.  If that is too scary to contemplate, then try using the PC-BSD
installer to install FreeBSD -- it lets you set up mirrors or ZFS from a
menu system, and can install plain FreeBSD as well as PC-BSD:

> now they said us that the only way for having backup of DATA in this
> condition is set up a scheduled task to put back up of data in the
> second HDD .

Well, this is really unsatisfactory and your colleagues should be ashamed.

First of all, RAID1 is not *backup*.  If you accidentally delete a file,
it will be removed from both of the mirrored drives.  The thing that
RAID1 gets you is resilience to disk failure: one of your drives going
'pop' will not result in the system crashing or any service interruption.

Backup of the system should be arranged through some other means: there
are many programs available to do the job in the base system or the
ports -- personally I like tarsnap, which will backup your data to the
cloud (Amazon flavoured cloud, that is) for a very reasonable rate.



Dr Matthew J Seaman MA, D.Phil.

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