[plug] recommendations for Debian server with hardware raid

Adrian Woodley Adrian at Diskworld.com.au
Tue Oct 23 19:25:04 WST 2012

Thought I should put in a plug for software RAID. Depending on your 
budget, software RAID can offer a compelling alternative.

The biggest advantage as I see it is future-proofing. In the event of a 
catastrophic failure with your hardware, the drives in a software RAID 
can be easily pulled and spun up on another machine, without any loss of 
data (assuming no damage to the drives themselves). This cannot always 
be said about hardware RAID, where even RAID controllers from the same 
manufacturer are not guaranteed to be able to rebuild an existing array 
from another controller.

Software RAID doesn't even care about architecture; I regularly pull the 
drives from my ARM based NAS and mount the array on my PC.

At the lower end of town, the performance difference between software 
and hardware RAID is negligible. Unless your controller card has a large 
amount of cache (which means it also needs on-board battery backup), 
you're unlikely to see any great performance benefit.

Lastly, software is incredibly flexible. Extra drives can be easily 
added to an existing array, including changing the RAID layout. Coupled 
with LVM, software RAID provides a very powerful drive management 
system. Infact, if managed carefully, many RAID manipulations such as 
growing an array or replacing drives can be performed online, without 
taking either the filesystem, array or even the server offline. The same 
can rarely be said about hardware RAID.

My one piece of advice for hardware RAID is, whatever you get, buy two. 
Put one in the cupboard for when your controller inevitably dies and you 
scream in desperation as your precious data disappears in a mess of blocks.

(This also ignores all the interesting things which can be done with 
modern filesystems, such as ZFS and BTRFS, which implement many 
RAID-like features).


On 23/10/12 09:40, Paul Dean wrote:
> Hi Andrew,
> I just got a HP DL385 G2 with a P400 Raid card in it.
> Whacked Wheezy on it, and grabbed the debs from HP repo, and loaded the cciss modules from stock kernel, hey presto all good.
> A little weird how it lists the drives, like old unix days, but it runs smooth and fast.
> iLO monitoring and extras run well, all round a good server.
> --
> Thanks
> Paul Dean.
> "Life is not WHAT you make it, it's WHO you have in it..."
> On Mon, 22 Oct 2012 20:57:54 +0800
> Andrew Furey <andrew.furey at gmail.com> wrote:
>> On 22 October 2012 18:42, Geoffrey Richards <Geoff at 79.com.au> wrote:
>>> Does anybody have any recommendations for a Debian based server supporting a
>>> hardware raid?
>> [snip]
>>> HP ML150 G6 witha smart array p410
>> You shouldn't have any issues with that, although you may need to add
>> "nomodeset" to your boot options (we do on the DL380s these days).
>> Andrew
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