[gentoo-user] Software RAID vs "Fake" RAID

[gentoo-user] Software RAID vs "Fake" RAID

[Yahya Mohammad]

Hi list,

I'm setting up a new desktop machine with RAID 0. The motherboard I
bought supports the so-called "Fake" RAID, which offloads most of the
processing to the system CPU. What are the pros and cons of using this
as opposed to  pure software RAID?

Re: [gentoo-user] Software RAID vs "Fake" RAID

[Neil Bothwick]

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On Mon, 27 Apr 2009 16:18:39 +0400, Yahya Mohammad wrote:

> I'm setting up a new desktop machine with RAID 0. The motherboard I
> bought supports the so-called "Fake" RAID, which offloads most of the
> processing to the system CPU. What are the pros and cons of using this
> as opposed to  pure software RAID?

The advantage of FakeRAID is that you get to depend on a Windows-only
driver that only works with your motherboard and will prevent the RAID
working if the motherboard files and you try to connect the drives to a
different system. For some reason,this gives Windows users a warm, fuzzy
feeling.


-- 
Neil Bothwick

Bumper Sticker: If you can read this, you are in phaser range.

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Re: [gentoo-user] Software RAID vs "Fake" RAID

[Andrei Susnea]

Neil Bothwick wrote:
> On Mon, 27 Apr 2009 16:18:39 +0400, Yahya Mohammad wrote:
>
>   
>> I'm setting up a new desktop machine with RAID 0. The motherboard I
>> bought supports the so-called "Fake" RAID, which offloads most of the
>> processing to the system CPU. What are the pros and cons of using this
>> as opposed to  pure software RAID?
>>     
>
> The advantage of FakeRAID is that you get to depend on a Windows-only
> driver that only works with your motherboard and will prevent the RAID
> working if the motherboard files and you try to connect the drives to a
> different system. For some reason,this gives Windows users a warm, fuzzy
> feeling.
>
>
>   
Maybe you want pure hardware raid that's a pci(-e) slot that has a chip 
doing all the parity calculations plus a battery keeping data that 
didn't manage to write in case of a power failure. That's the best option.
For a mb in order to have fake raid capabilities from my understanding 
it has to have a raid chip itself but still most of the calculation is 
done by the CPU.
Software raid can be done OS dependant... and you don't need any 
hardware or chips for that, it's a form of OS fooling itself instead of 
the MB fooling the OS (fake one).

 From my experience with fake raid 0 on 2 hdd's the speeds would be very 
nice when talking about small files, but for files with 1gb or more the 
writing speed would decrease as the parity calculations get more 
complicated.

Re: [gentoo-user] Software RAID vs "Fake" RAID

[Volker Armin Hemmann]

On Montag 27 April 2009, Andrei Susnea wrote:
> Neil Bothwick wrote:
> > On Mon, 27 Apr 2009 16:18:39 +0400, Yahya Mohammad wrote:
> >> I'm setting up a new desktop machine with RAID 0. The motherboard I
> >> bought supports the so-called "Fake" RAID, which offloads most of the
> >> processing to the system CPU. What are the pros and cons of using this
> >> as opposed to  pure software RAID?
> >
> > The advantage of FakeRAID is that you get to depend on a Windows-only
> > driver that only works with your motherboard and will prevent the RAID
> > working if the motherboard files and you try to connect the drives to a
> > different system. For some reason,this gives Windows users a warm, fuzzy
> > feeling.
>
> Maybe you want pure hardware raid that's a pci(-e) slot that has a chip
> doing all the parity calculations plus a battery keeping data that
> didn't manage to write in case of a power failure. That's the best option.
> For a mb in order to have fake raid capabilities from my understanding
> it has to have a raid chip itself but still most of the calculation is
> done by the CPU.
> Software raid can be done OS dependant... and you don't need any
> hardware or chips for that, it's a form of OS fooling itself instead of
> the MB fooling the OS (fake one).
>
>  From my experience with fake raid 0 on 2 hdd's the speeds would be very
> nice when talking about small files, but for files with 1gb or more the
> writing speed would decrease as the parity calculations get more
> complicated.

there is no parity with raid 0.

Re: [gentoo-user] Software RAID vs "Fake" RAID

[Simon]

I would recommend software raid.  Because it's made by some great
folks in the linux community and it is a project in development (so
you can get lots of support and updates, though it is very stable and
is used in many prod systems).

Also the tool 'mdadm' combined with the output of /proc/mdstat gives a
very good flexibility and ease of administering the raid.

I wouldnt touch fakeraid, and i would only use hardware raid for a
serious purpose (ie business) since it costs a lot and efficiency gain
can only mean something in a serious project.  (I'm using several
raids on USB keys, dont laugh!, for my small 4gb EeePC, it raid6 has
been working super fine on software linux raid).

Simon

On Mon, Apr 27, 2009 at 8:18 AM, Yahya Mohammad <mfyahya@gmail.com> wrote:
> Hi list,
>
> I'm setting up a new desktop machine with RAID 0. The motherboard I
> bought supports the so-called "Fake" RAID, which offloads most of the
> processing to the system CPU. What are the pros and cons of using this
> as opposed to  pure software RAID?
>
>



-- 
When Earth was the only inhabited planet in the Galaxy, it was a
primitive place, militarily speaking.  The only weapon they had ever
invented worth mentioning was a crude and inefficient nuclear-reaction
bomb for which they had not even developed the logical defense. -
Asimov

Re: [gentoo-user] Software RAID vs "Fake" RAID

[Paul Hartman]

On Mon, Apr 27, 2009 at 9:14 AM, Simon <turner25@gmail.com> wrote:
> I would recommend software raid.  Because it's made by some great
> folks in the linux community and it is a project in development (so
> you can get lots of support and updates, though it is very stable and
> is used in many prod systems).

I'm using software RAID5 (with SATA hard drives) for a couple years
and -- without having any drive failures so far -- it seems to work
well. I've got dmcrypt on top of it and performance is pretty
transparent for the most part. Having core 2 duo helps, I guess. :)

It was dead simple to set up, but I have (thankfully) not run into any
drive failures so far. I should really prepare an off-line document
with the recovery procedure should that happen. I'm not sure off the
top of my head (other than pull bad drive, replace with new drive). In
fact I need to make sure I know which drive is which!

It has survived several crashes/power outages. For my RAID5 (four
500gb drives) it took about 90 minutes for the raid to verify after
such incidents. I know there are benefits to hardware RAID but for low
cost/low importance (it's my home PC) the software RAID is good enough
for me.

Re: [gentoo-user] Software RAID vs "Fake" RAID

[Simon]

> It has survived several crashes/power outages. For my RAID5 (four
> 500gb drives) it took about 90 minutes for the raid to verify after
> such incidents. I know there are benefits to hardware RAID but for low
> cost/low importance (it's my home PC) the software RAID is good enough
> for me.

Software raid is perfect for a situation like this, also, the choice
for raid5 (or raid6) is good because while it provides redundance
(security when a drive fails) it also supports growing (you can make
the array bigger by adding drives), as long as the file system on it
supports growing.

I'm not sure how 'growing' support is handled in hardware raid and i'm
ready to believe it is inexistant in fakeraid...  but I'm saying so
without knowing...

Simon

Re: [gentoo-user] Software RAID vs "Fake" RAID

[Alan McKinnon]

On Monday 27 April 2009 14:18:39 Yahya Mohammad wrote:
> Hi list,
>
> I'm setting up a new desktop machine with RAID 0. The motherboard I
> bought supports the so-called "Fake" RAID, which offloads most of the
> processing to the system CPU. What are the pros and cons of using this
> as opposed to  pure software RAID?

There are no pros that I have ever seen and plenty of cons. Notably - 
performance sucks.

You are almost always better off using software RAID. Big plus - you can 
actually configure it to get a result closer to what you want as opposed to 
what the firmware manufacturer wants you to have.


-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] Software RAID vs "Fake" RAID

[Hazen Valliant-Saunders]

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Ok,

1. Motherboard Raid is often "Fake Raid"
2. In Gentoo the Software Raid fucntions for Linux are probably faster than
your motherboard's
3. Having had and seen issues with mother board raid I'd suggest using the
mdtools. Since there is a FAR LARGER support base; that way if somthing goes
awry you'll have a far larger pool of knowledge to draw from.

When Considering Raid always look to see if you have a MB that has it's own
XOR implemented in silicon, these are a little pricy but they are the
"Engine" that speeds up the whole checksumming process.

Server Motherboards and high end workstations will have integrated RAID
controllers from repudible providers (LSI, Adaptec, AMI...) and even those
break down and forget configuration's some times.

If you are going to do a whole bunch of storage on the cheap the software
raid is fine, and if you have a quad core you won't even notice the
overhead.

On Mon, Apr 27, 2009 at 11:35 AM, Alan McKinnon <alan.mckinnon@gmail.com>wrote:

> On Monday 27 April 2009 14:18:39 Yahya Mohammad wrote:
> > Hi list,
> >
> > I'm setting up a new desktop machine with RAID 0. The motherboard I
> > bought supports the so-called "Fake" RAID, which offloads most of the
> > processing to the system CPU. What are the pros and cons of using this
> > as opposed to  pure software RAID?
>
> There are no pros that I have ever seen and plenty of cons. Notably -
> performance sucks.
>
> You are almost always better off using software RAID. Big plus - you can
> actually configure it to get a result closer to what you want as opposed to
> what the firmware manufacturer wants you to have.
>
>
> --
> alan dot mckinnon at gmail dot com
>
>


-- 
Hazen Valliant-Saunders
IT/IS Consultant
(613) 355-5977

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Re: [gentoo-user] Software RAID vs "Fake" RAID

[Yahya Mohammad]

On Mon, Apr 27, 2009 at 05:35:45PM +0200, Alan McKinnon wrote:

> There are no pros that I have ever seen and plenty of cons. Notably - 
> performance sucks.

First, thanks very much to everyone who replied.

The only reason I considered the motherboard RAID was that I could have
an XP partition and install an ext2 driver to access my Gentoo
partitions. As far as I know, a filesystem in a linux software raid
cannot be accessed from windows.

After reading the replies here, I'm going to go ahead with linux
software raid. Accessing my linux partitions from windows isn't very
important for me, as I only use XP for occasional gaming.

Re: [gentoo-user] Software RAID vs "Fake" RAID

[Simon]

> The only reason I considered the motherboard RAID was that I could have
> an XP partition and install an ext2 driver to access my Gentoo
> partitions. As far as I know, a filesystem in a linux software raid
> cannot be accessed from windows.
>
> After reading the replies here, I'm going to go ahead with linux
> software raid. Accessing my linux partitions from windows isn't very
> important for me, as I only use XP for occasional gaming.

And even then last time i checked windows support for ext2 FS wasnt so
great.  I personnally do all file transfer using linux (which works
fine with windows' fat FS, i dont use ntfs because it used to lack
write support long ago).

That is, in windows, i would move the files in a folder created on the
desktop, and then in linux, i would mount the windows drive and
copy/move the files in
/mnt/windrive/Documents*/simon/Desktop/folder_for_linux/.

If you wish to setup windows on a raid, you might consider the
fakeraid for that?  But if you use it for gaming i dont think raid is
advisable, doing backups should be sufficient, IMO.

HTH, Simon