Re: Supermicro SAS controller
On Sat, 05 May 2012 10:44:02 +0000, Ramon Hofer wrote:
> On Fri, 04 May 2012 15:38:10 +0000, Camaleón wrote:
(...)
>> http://hwraid.le-vert.net/wiki/LSIMegaRAIDSAS
>>
>> Ufff, I was not aware of this:
>>
>> ***
>> There is currently no known opensource tool for theses cards.
>> ***
>>
>> How, how bad... in contrast, 3ware seems to fully support open source,
>> or at least that's what it can be read here:
>>
>> http://hwraid.le-vert.net/wiki/3Ware
>>
>> ***
>> 3Ware supports Linux and provide an opensource kernel driver which has
>> been part of Linux for ages
>> ***
>>
>> This is something to reconsider.
>
> Yes, this is really not what I wanted to read :-o
It was also unknown to me... I thought this manufacturer was providing
more support to linux other than having a bunch of binaries at their
site :-/
> So I think I'll just go for the LSI card and use mdadm. The 3Ware card I
> found at my dealer was twice the price of the LSI...
Well, despite the card manufacturer does not provide an open source
driver, you can still use the binary utilities built for Debian,
available at the mentioned site. You can always reconsider moving to
mdadm if something goes wrong or if you get into some trouble while
setting up the hardware RAID card.
Still, my 0.2 cents go for a hardware raid :-)
>> Just a note of caution here.
>>
>> RAID 5 with big hard disks can be a real pain and a real problem. If
>> one of the arrays go down, the rebuilding operation can take up to
>> "days" (depending on the controller's capacity) and if while the RAID
>> is rebuilding a second disk of the array is also down for whatever
>> reason (it can be a false possitive) you can't recover your data, at
>> least not that easily. That's why most people is switching from raid 5
>> to raid 6, it adds an extra of security with no remarkable drawbacks.
>
> That's true.
>
> On the other hand it isn't possible to have different disk sizes in a
> raid 6 neither.
I think yes, that you can, but only the lowest of the disk capacities
will be used (this applies to all of the RAID levels). Software RAID has
not such limitaion because you can mirror partitions, instead.
> So my plan seems still reasonable to me to have several 4 disks raid 5
> arrays. Like that I'm flexible to add bigger disks in future as they
> become cheaper and still can keep my old 1.5 TB disks. And if I would go
> for raid 6 with the 4 disk array I would loose a third of the capacity.
(...)
You've been warned :-)
Greetings,
--
Camaleón
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