Are built in RAID controllers worse than store bought ones?

[jf1288]

The mobo i think im going to buy has a built in raid controller. For raid 0, does it make a difference if the controller is built into the mobo, or if it is a seperate card? I heard that some raid controllers have their own memory slot, does that mean that a built in one leeches from system memory?

[Ugly_Jim]

If it's an Intel onboard raid controller, there isn't much better out there for raid 0,1,0+1. On the other hand, I have an NF7-S, and the Silicon Image controller is probably the worst controller ever. It wouldn't even work until I rolled back the bios, and it's also significantly slower than the Intel RAID controller. I'm thinking about buying an actual controller card and using that.

edit: I forgot the best part: HDtach shows 25% cpu utilization.

[E4g1e]

If it's an Intel onboard raid controller, there isn't much better out there for raid 0,1,0+1. On the other hand, I have an NF7-S, and the Silicon Image controller is probably the worst controller ever. It wouldn't even work until I rolled back the bios, and it's also significantly slower than the Intel RAID controller. I'm thinking about buying an actual controller card and using that.

edit: I forgot the best part: HDtach shows 25% cpu utilization.
Unfortunately, there are many store-bought PCI SATA (Serial ATA) controller cards on the market that use the Silicon Image controller chip that you've criticized. And no matter which controller chip that the controller card uses, its performance will be hampered by the PCI bus itself: Every one of the add-in PCI SATA controller cards will be significantly slower than the native Intel SATA controller (since almost all current SATA controller cards use the relatively ancient, 32-bit, 33MHz PCI bus) - the theoretical maximum burst rate of 150 MB/sec for SATA is mismatched to the maximum theoretical burst rate of only 133 MB/sec for the entire 32-bit, 33MHz PCI bus (the latter of which is usually clogged with bandwidth-hogging devices such as today's advanced soundcards).

Furthermore, alas, Silicon Image is pretty much the only brand of add-in PCI-based SATA controller chips that were designed for SATA natively. The other brands of "SATA" controller chips used in SATA controller cards are NOT true SATA controller designs! Those are actually PATA (Parallel ATA) designs that had been modified to support SATA devices! If anything, the SATA controller cards based on one of those other controller chips will be even slower than the Silicon Image controller.

[absolut][krypkn0t]

if you get an add-in get 3ware and nothing else... they have proven themselves to be the best cards for anything ATA/IDE and he is right about the 150/133 mismatch... i'd get a card that has a good onboard raid solution until they come out with motherboards that have pci-x slots on them and get a pci-x controller card... by then sata should be up to 300 i think also

[jf1288]

ok cool, thanks

[Cardboard Hammer]

[krypkn0t']if you get an add-in get 3ware and nothing else... they have proven themselves to be the best cards for anything ATA/IDE and he is right about the 150/133 mismatch... i'd get a card that has a good onboard raid solution until they come out with motherboards that have pci-x slots on them and get a pci-x controller card... by then sata should be up to 300 i think also

Boards with PCI-X slots are already available, but they're only on workstation or server boards and probably will never show up on desktop boards. You probably meant PCI-Express, which is very different from PCI-X. (PCI-X is a faster, wider version of PCI. PCI-Express is serial instead of parallel and is incompatable with both PCI and PCI-X.) Boards with PCI-Express slots should start becoming available before too much longer.

[Ice Czar]

Are built in RAID controllers worse than store bought ones?


almost invariably

RAID the lesser levels (http://www.lostcircuits.com/hdd/hdd7/) @ Lost Circuits, Ask the Disc Spins Series
Different “Categories” of RAID
In general, on we need to distinguish between three different categories of RAID, namely:

1. Standalone RAID solutions for mass storage in the backplane of servers (fiber channel-attached) or Network-Attached Storage (NAS) connected via Firewire or Gigabit Ethernet.

2. RAID functionality via separate Host Bus Adapter (HBA) cards using PCI, PCI-X (64bit / 66 MHz) or PCI-Express (3GIO) interface.

3. RAID controller integrated on the mainboard level. Often called RAID-lite because of limited functionality, except for dedicated Server boards. RAID on Mainboard (ROMB).


there are a great many different variables at the HBA level
as mentioned the throughput of the bus with the various slots, in addition there is the stripe width (number of drives) RAID level,
the protocol's command optimizations and the interface speed, the drives, and the controller itself
*SCSI (P&S), ATA (P&S), FC, USB, Ethernet, Firewire

Cardboard Hammer re: PCI-X
What a relief! For a second there I thought I was a victim of an elaborate hoax!
:p :p :p

jk

[E4g1e]

almost invariably
Well, that may be true, as far as RAID itself is concerned. However, an add-on PCI RAID card is invariably much worse than expensive dedicated full-sized RAID solutions. The better RAID cards require a 64-bit, 66MHz PCI-X slot for full potential (but may work on conventional 32-bit, 33MHz PCI slots with reduced performance and/or features).

On the other hand, when it comes to Serial ATA (SATA) controllers, most add-in PCI cards are no better than the poorer-performing built-into-the-motherboard SATA controllers. That's because the PCI SATA controller cards that I've seen use the exact same chipsets as the on-motherboard ones - and those from 3ware, HighPoint and Promise are not true SATA controller chips, but are actually Parallel ATA (PATA) controller chips that use a third-party translator to convert PATA signals to SATA. Furthermore, the lower-end SATA controller cards from Adaptec (a household name in SCSI adapters, of all brands) are pretty much just ordinary Silicon Image Si3512R- or Si3114R-based PCI controller cards. And the SATA controller cards that perform appreciably better than onboard all cost significantly more money than what most SATA RAID-integrated motherboards themselves do.

Back to your question, jf1288:

RAID 0 is not true RAID at all, to begin with, since it provides no redundancy at all whatsoever. Even the built-into-the-motherboard RAID controller will do. In fact, the higher-end RAID controllers will not do RAID 0 at all - they require three or more hard drives to even work at all, since they can only do the higher levels of RAID such as RAID 5. And those higher-end RAID controller cards are generally SCSI-based, with a few SATA-based controller cards available (but hardly any PATA-based controllers exist at all at that level).

[Ice Czar]

Well, that may be true, as far as RAID itself is concerned. However, an add-on PCI RAID card is invariably much worse than expensive dedicated full-sized RAID solutions.

.....for the desktop or workstation

enterprise storage is another ball o wax, where having the data online 24\7 with the ability to suffer more than one drive failure, and be part of a SAN node almost dictates such an array

addressing the 2nd point your addressing the interface but leaving out the internal performance factors of the HDDs, no single HDD can even come close to the PATA interface speed (100>133MB/s) so in a dual channel ROMB be it PATA or SATA
its not that big a deal (single ATA HDD STR (sustained transfer rate) being at best aroud 50MB/s)

as you point out there are alot of variable in the controllers themselves, and they arent the sole consideration (again as you pointed out)
when you do step into more channels with the right RAID level
the bus width and speed can become an isssue, I consider the true dividing line between a deaktop and a workstation \ server to be, a desktop has just 32bit 33MHz PCI slots
and a Workstation has 64bit\66MHz to PCI-X 64bit 133MHz PCI slots or a SCSI ROMB or zero channel RAID Ui60 or U320 channel attached to a 64bit bus

SATA as implemented on motherboards currently really doesnt approach that kind of throughput (emulated or native), and with good reason, there are few aps that require it, you either need a multi-user environment (server) or a workstation level ap like real time high resolution video capture and editing, in which case the upgrade to a workstation board with a 64bit PCI slot is dictated

but with PCI expresss that line is going to blur, but for right now, using a multi-channel (4 or more) RAID card as a RAID 0, is going to be bottlenecked, but a dual Channel SATA RAID 0 is bottlenecked at the HDD performance

and thats assuming we are talking RAID 0, I run a 32bit RAID card in RAID 5
completely different objective

the reason I said almost invariably is that for a RAID 0 (again from the lesser RAID Levels (http://www.lostcircuits.com/hdd/hdd7/2.shtml))
Whether any given RAID solution is Hardware or Software often boils down to a matter of semantics. That is, by definition, any dedicated hardware RAID channels will qualify the array as Hardware RAID. However, often enough another distinction is made based on the presence or absence of a dedicated XOR processor. That is, any hardware RAID controller without the additional controller will often be referred to as software RAID, in other words, there is a grayzone.

which would lead us into the optimizations in command queing in PATA vs SATA, vs SCSI
the differences in the protocols themselves, and how the controllers are able to take advantage of them, what kind of load they place on the CPU, where as you pointed out the "expensive" SATA do quite a good job, but still only as good or slightly less than a good SCSI controller, which often will have substantially less CPU impact

all taken within the 133MB/s parameter, and the comparitive HDD internal performance parameter, the weighing of these variables being very complex

which is why I sort of prodded it with a stick and ran away :p

but the real reason from the majority of the members point of view, why a card is better than onboard, you can migrate it ;)
lost my first array when the mobo died, and I opted to not buy my next board based on its RAID chip