Software raid VS hardware raid

[Daniel Feenberg]

On Mon, 28 Jan 2013, Per olof Ljungmark wrote:

> On 01/28/13 21:43, Artem Kuchin wrote:
>> Hello!
>>
>> I have to made a decision on choosing a dedicated server.
>> The problem i see is that while i can find very affordable and good
>> options they do not
>> provide hardware raid or even if they do it is not the best hardware for
>> freebsd.
>> The server base conf is 8core 32gb ram 2.8+ ghz.
>> So, maybe someone has personal experience with both worlds and can tell
>> if it
>> really matters in such configuration if i go for software raid. What are
>> the benefits
>> and what are the negatives of software raid? How much is the performance
>> penalty?
>> I am planning to use mirror configuration of two SATA 7200rpm 2TB disks.
>> Nothing fancy.
>> File system planned is UFS with journaling.
>>
>
> I won't delve into detail here but if the data is important HW RAID is
> where you want to be. Perhaps you could give us a little more details

A problem with HW RAID is that if the controller breaks, you need to get 
an identical controller to replace it, or the data will be lost. With 
software raid, you can read the data on any machine that will boot 
FreeBSD. That is a great convenience compared to searching eBay for an 
obsolete controller with the proper rev level.

We haven't noticed any speed disadvantage on modern multi-core hardware 
and RAID 1. The advantages of HW raid escape me - I understand that 
years ago it provided OS independence and reduced CPU load, but it no 
longer provides the former, and with 8 cores do you need the latter while 
waiting for a disk platter to spin?

ZFS is worthwhile, too, especially since you have a good amount of memory. 
That would give you snapshots and some other desirable features, such as 
background scanning for defects that UFS doesn't have.

> about what the purpose of the server is? Mission-critical or low cost?
> Those two tends to be mutually exclusive...

Surely the presence of SATA drives shows that low cost is essential.

Mirroring and ZFS provide very important advantages. HW raid seems to fill 
a much needed gap (apologies to Brian Kernigan).

daniel feenberg


>
> We are HP-only but have good experience from LSI as well.
>
> Just my $0.02.