Re: SCSI Disk/Controller advice please
From: Henrique de Moraes Holschuh (hmh_at_debian.org)
Date: 10/31/04
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Date: Sun, 31 Oct 2004 13:00:02 -0300 To: debian-user@lists.debian.org
> >you could try higher RAID levels (RAID 5) for data integrity. RAID 1
> >will only mirror disks - and that would also mean should there be
> >errors in one disk it gets propagated to the mirror as well.
Indeed this is false. It also shows a complete lack of understanding the
very basic principles of RAID, so please don't waste much of your time
trying to figure out what the guy meant, he is seriously confused and needs
to read more on RAID first.
> (suposing that it does happen) does not happen with RAID5. Why? With
> RAID5 you "checksum" data and in RAID1 you mirror sectors?
You can detect inconsistencies in a non-degraded (and redundant) RAID
regardless of RAID level (whether your RAID implementation will do it is
something else entirely). RAID by itself will not be capable of detecting
inconsistencies on a degraded (non-redundant) RAID.
RAID does not have checksums, it has error-correction codes. You can call
it "parity" if you wish (although that is not strictly correct, IMHO). But
don't call it "checksum", please. It confuses those who don't know what
they are talking about in the first place.
> I've googled for these problems you claim in RAID1 and haven't found
> nothing stating that these things could happen!
Because they cannot.
Oh, a particular RAID1 setup could have much worse failure tolerance than
another RAID5 setup, but that's all due to bad design or bad implementation
on that singular RAID1 setup in the first place.
>just confirm this: There is no SCA controllers. The controllers have
> 68 pins wich connect to the hot-swap rack (wich will also receive power
> from a regular power cable) and the hot-swap rack will have the sca
> connector to connect to a sca disk. Is that it?
That is correct AFAIK.
-- "One disk to rule them all, One disk to find them. One disk to bring them all and in the darkness grind them. In the Land of Redmond where the shadows lie." -- The Silicon Valley Tarot Henrique Holschuh -- To UNSUBSCRIBE, email to debian-user-REQUEST@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmaster@lists.debian.org
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