On 07/09/14 10:43 PM, Valeri Galtsev wrote:
On Sun, September 7, 2014 9:30 pm, John R Pierce wrote:
On 9/7/2014 7:19 PM, Dave Stevens wrote:
I want to set up a new CentOS install using version 7 and would like
to experiment with various RAID levels. Anyone care to point out a
tutorial?
how many drives do you have for this experiment? whats the target
usecase for the file systems on the raid(s)? whats the level of data
resiliance required by said use case?
Raid only protects against one specific sort of failure, where an entire
disk drive fails. It doesn't protect against data corruption, or
system failure,
Even more: system failure or power loss is more likely to destroy all data
on software RAID than on a single drive when there is a lot of IO present
(to the best of my understanding, loss of cache software RAID is using is
more catastrophic compared to journaled filesystem under same
circumstances - somebody may correct me). So, there may be worth thinking
about hardware RAID.
Just my 2c.
Valeri
Valeri makes an excellent point, which I would like to elaborate on;
Hardware RAID *with* flash-backed/battery-backed cache. I find it
endlessly fascinating how many machines out there have hardware RAID
with BBU/FBU. When using write-back caching without a battery leaves you
in no better position.
Note that if you do get hardware RAID with BBU/FBU, be sure the cache
policy is set to "Write-Back with BBU" (or your controllers wording).
The idea here is that, if the battery/caps fail/drain, the controller
switches to write-through (no) caching.
I'm not so familiar with software RAID, but I would be surprised if
there isn't a way to force write-through caching. If this is possible,
then Valeri's concern can be addressed (at the cost of performance).
digimer
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Digimer
Papers and Projects: https://alteeve.ca/w/
What if the cure for cancer is trapped in the mind of a person without
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