Re: Supermicro SAS controller
On Fri, 04 May 2012 10:48:36 +0000, Ramon Hofer wrote:
> On Thu, 03 May 2012 20:27:02 +0000, Camaleón wrote:
>> There's some useful information in one of the links I sent before:
>>
>> http://wiki.debian.org/LinuxRaidForAdmins
>
> Maybe I miss something but the page doesn't say anything about cli tools
> of the megaraid cards :-?
Yes... no info is also info after all. Not the one you'd like to read but
that's how it is :-). Anyway, the page can be simply outdated or lacking
from that specific information.
Also, the expanded information on the "megaraid_sas" driver points to the
page you sent before:
http://hwraid.le-vert.net/wiki/DebianPackages
Where you can find a set of tools for your driver ("megaclisas-status"
and "megacli") as well as more information about the LSI controllers and
the driver status:
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.
>> In case of disasterous raid failure you depend completely on the
>> manufacturer and what are the option they can provide (although data
>> recovery can be usually done at professional labs).
>
> My data isn't so important that it would justify restoring it with
> professional help.
>
> Still I have to do backups of the really important stuff to dvd or a
> seperate external drive...
Yes, and very good point. A RAID system can never substitute the backups,
they have to be set in paralel (RAID cares about hardware issues while
backups about software/logical/user errors).
>> Just an additional note. By reading the chosen card specs it seems it
>> does not support a RAID 6 level (which is better than RAID 5 because it
>> allows the failure 2 disks) so that can be a handycap.
>
> This should be no problem. I plan to use four slots without raid for
> mythtv.
> I already have a 4x 1.5 TB disks raid 5 and another 4x 2 TB disks raid
> 5. When I want to add more disks I can e.g. go for 3 TB disks and set 4
> of them up as another raid5.
> Like this I can use disks with different sizes.
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.
> I'm thinking of combining the arrays then to a lvm... But I don't know
> if this is a good idea as it adds more complexity :-?
Yes, it will be a good idea (it will allow you to manage your volumes in
a more flexible manner) and yes, it will add an extra layer of complexity
(RAID+LVM) :-)
Greetings,
--
Camaleón
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