Re: SCSI Disk/Controller advice please
Hi Paolo, Alvin, Pigeon, Ron & Tim, thanks for all the replies...
Paolo Alexis Falcone wrote:
[snip]
Which are the tradeoffs of hard vs software raid1? What happens/How do
we proceed if 1 disk fails (how do we know it, how do we replace/resync
them?)
[snip]
Do note though that RAID 1 won't help you that much - it's better if
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.
Alvin, first off all I'm aware of high availability solutions (I've done
my master thesis on those setups), but together with HA solutions we can
use RAID anyway...
Alvin and Paolo, I'm quite stunned with these claims that "errors on one
disk will be propagated to the other when using RAID1". It still makes
no sense to me that something like that could happen. Quoting Tim:
"
>>problem with raid1 ( aka mirror )
>> - if one disk goes bad, the other disk will copy that bad info
>> onto the good disk .... the whole point of mirror, both disk
>> is identical
Completely false. Physical disk errors mirrored by raid? No, No,
No. Fat fingered deletes? Yes.
"
Paolo, as far as I understand your statements, you state this behaviour
(suposing that it does happen) does not happen with RAID5. Why? With
RAID5 you "checksum" data and in RAID1 you mirror sectors?
I've googled for these problems you claim in RAID1 and haven't found
nothing stating that these things could happen!
Altough I'll not be going to SCA (as it appears to add somewhat
significant $$$ to my environment where I don't neet 24/7 availability),
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?
Thanks
Joao Clemente
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