Onboard Raid (e.g. ICH10R) vs. Raid Controller card

[gigaflux]

Hi,

I'm thinking about building up a new computer. I want to do some video
editing and cutting with it, maybe a little bit more than usally is
done at home but certainly it's just a hobby not something I have to
earn money with. That said I want to add that I want a decent machine
but still I have to look at the costs.

One of the parts I don't know much about is the RAID controller. I
would like to have a RAID 5 with three drives (at the beginning),
since it seems to be a good compromise between safety and speed. I
know that software-only RAIDs (like provided by the OS, eg. Win XP)
are crap, but what are the pros and cons between hybrid Raid
controllers (like the ICH10R) and real hardware raid controllers
concerning the performance? The real question is: If I spent addtional
300 € for that piece of hardware (say 20% of the whole computer) , do
I get a better performance that is really worth those 20%?

Certainly this question is quite ambiguous, so I may add that I'm
looking for a quad core desktop computer (no server). And still I'm
sure that there is no general answer. Nevertheless your opinions to
that issue would be appreciated *g* Also: I didn't find any
performance tests for hybrid raid controllers (ICH8/9/10R) with more
than two drives oder more than one array (or even a comparative test
between hybrid and real controllers). Since I am quite new to this
issue it might be that I just don't know where to look, any
suggestions?

Thank you in advance,
Flynx

 

[Arno Wagner]

Hi,

I'm thinking about building up a new computer. I want to do some video
editing and cutting with it, maybe a little bit more than usally is
done at home but certainly it's just a hobby not something I have to
earn money with. That said I want to add that I want a decent machine
but still I have to look at the costs.

One of the parts I don't know much about is the RAID controller. I
would like to have a RAID 5 with three drives (at the beginning),
since it seems to be a good compromise between safety and speed. I
know that software-only RAIDs (like provided by the OS, eg. Win XP)
are crap,

They are not generally. For Linux they are very reliable and fast.
Also Softwre RAID removes the need for a spare controller.

but what are the pros and cons between hybrid Raid
controllers (like the ICH10R) and real hardware raid controllers
concerning the performance? The real question is: If I spent addtional
300 ? for that piece of hardware (say 20% of the whole computer) , do
I get a better performance that is really worth those 20%?

Unlikely for the array size you are looking at. The Intel
matrix RAID controllers, BTW, are incompatible with Linux
and I know somebody with one that is plagued by frequent
rebuilds, despite the disks being fine.

Certainly this question is quite ambiguous, so I may add that I'm
looking for a quad core desktop computer (no server). And still I'm
sure that there is no general answer. Nevertheless your opinions to
that issue would be appreciated *g* Also: I didn't find any
performance tests for hybrid raid controllers (ICH8/9/10R) with more
than two drives oder more than one array (or even a comparative test
between hybrid and real controllers). Since I am quite new to this
issue it might be that I just don't know where to look, any
suggestions?

If you want hardware RAID, I would recommend 3ware. If their
controllers are too expensive for you, you might consider
going with software RAID.

Arno

 

[Flynx]

Hi Arno,

[...]

They are not generally. For Linux they are very reliable and fast.
Also Softwre RAID removes the need for a spare controller.

Hm, true. But I need the CPU performance for the rendering process and
I wonder how much CPU power has to be spent for the XOR calculation of
the RAID 5. If that is no issue, I will go for the software solution
(well, for the hybrid option, or is there any disadvantage using the
ICH10R controller ? ).

Unlikely for the array size you are looking at. The Intel
matrix RAID controllers, BTW, are incompatible with Linux
and I know somebody with one that is plagued by frequent
rebuilds, despite the disks being fine.

I thought that I had read some statements about the linux
compatibility of these controllers ... well, since I am bound to WinXP
that's not a problem here.

You mentioned the array size. With how many drives in the array it
would make a difference? I will start with three drives, but will buy
more if the capacity is seriously draining. I don't know how much
performance is lost when using more then three drives and a software
or Intel matrix controller (that's what I called a hybrid controller).

If you want hardware RAID, I would recommend 3ware. If their
controllers are too expensive for you, you might consider
going with software RAID.

That's a clear statement! But let me repeat my question above: Would
you recommend a software-only solution? I would have thought the
hybrid (= Intel matrix) chips would lower the CPU load at least a
little bit.

Flynx

 

[Arno Wagner]

Hi Arno,

[...]

I know that software-only RAIDs (like provided by the OS, eg. Win XP)
are crap,

They are not generally. For Linux they are very reliable and fast.
Also Softwre RAID removes the need for a spare controller. [...]
If you want hardware RAID, I would recommend 3ware. If their
controllers are too expensive for you, you might consider
going with software RAID.

That's a clear statement! But let me repeat my question above: Would
you recommend a software-only solution? I would have thought the
hybrid (= Intel matrix) chips would lower the CPU load at least a
little bit.

CPU load will be low anyways. Linux on an Athlon 64 x2 5600+ has some
GBs/sec of RAID5 maximum thoughput, i.e. you will have something
like <10% (of one core) with typical disks. You should however
make sure to get a PCI-E (non-RAID) controller, or integrated
(non-RAID) controller attached to PCI-E. Otherwise the I/O bandwidth
can be a bottleneck, as PCI only reaches something like 80MB/s combined
for all data streams.

Of course, it is possible that Microsoft has messed up their software
RAID performance, like so many other things. Better check that. I
have no RAID under Windows and do not know.

Arno

 

[Arno Wagner]

Hi Arno,
[...]

I know that software-only RAIDs (like provided by the OS, eg. Win XP)
are crap,

They are not generally. For Linux they are very reliable and fast.
Also Softwre RAID removes the need for a spare controller. [...]
If you want hardware RAID, I would recommend 3ware. If their
controllers are too expensive for you, you might consider
going with software RAID.

That's a clear statement! But let me repeat my question above: Would
you recommend a software-only solution? I would have thought the
hybrid (= Intel matrix) chips would lower the CPU load at least a
little bit.

CPU load will be low anyways. Linux on an Athlon 64 x2 5600+ has some
GBs/sec of RAID5 maximum thoughput, i.e. you will have something
like <10% (of one core) with typical disks. You should however
make sure to get a PCI-E (non-RAID) controller, or integrated
(non-RAID) controller attached to PCI-E. Otherwise the I/O bandwidth
can be a bottleneck, as PCI only reaches something like 80MB/s combined
for all data streams.

Of course, it is possible that Microsoft has messed up their software
RAID performance, like so many other things. Better check that. I
have no RAID under Windows and do not know.

Arno

P.S.: As to hybrid, if you rely on any kind of hardware, you
typically need a second pice of that hardware for recovery if
the first one dies. There is limited support for RAIDs that have
different hardware RAID superblocks in Linux dm-raid and there
is also RAID recovery software, but my guess is unless you are
cash-starved, you should have that second controller/mainboard
ready. With pure software RAID, you typically can just move the
disks to a different machine and read them immediately or with
limmited hassle.

Arno