My motherboard, an Asus M4a79t Deluxe, advertises RAID 0/1/5 capabilities. My limited understanding is that onboard RAID is better than software RAID. Is this necessarily true? Is an onboard RAID controller closer in performance to a software controller or a dedicated hardware controller?
Hardware RAID, which means buying a RAID card, and installing it in your computer is good.
Software RAID is low performance, but it's reasonably stable, and pretty reliable.
"Onboard" RAID, which is the crappy RAID emulation built into your motherboard, has low performance, AND low stability.
I have used onboard RAID before, and I have always regretted it. You gain nothing, zero, zip, from using built in RAID emulation, no matter how much you paid for the motherboard. There is no optimization, there is no performance increase. Lose a drive in a RAID 5...It can take literally DAYS to rebuild it. Likewise checking an array for errors, and errors WILL happen, because it's not reliable.
If you use software RAID emulation, at least you can put the drives in another machine and have a good shot for recovering the RAID. With an onboard RAID emulator? Impossible.
"they are perfectly adequate for someone that wants a simple backup plan"
Remember, RAID is not a backup strategy, it's designed to increase performance and or reliability of your storage!
Backup means getting the data synchronized off of the RAID array(s) onto another storage device.
Google for "raid is not backup" for countless articles that discuss the myth :-)
In my opinion, on board RAID is in fact a software RAID. Most of the job is done by dedicated drivers installed in the operating system.
Depends on the RAID type. Been quite a while since I've seen benchmarks doing direct comparisons between pure software vs. on board, vs. dedicated, but from what I remember:
- Pure software is just a disaster. Avoid it whenever possible. You can get pretty reasonable performance with either a RAID1 or RAID0 setup using it, but it's just not worth the hassle to actually putting it in place.
- On board RAID 0 performance is comparable to a dedicated controller. RAID1 write performance is about the same as well. RAID1 read performance however appeared limited to single drive speed, where the better hardware controllers would stripe the data together like RAID0 for a faster throughput. RAID5 performance of on board is limited. Reasonable enough for something like a home media server, but the dedicated XOR hardware of the controller card makes the on board look anemic.
Like I said though, it's been a good 3 or 4 years since I've really read anything about the performance of on board controllers, and we've had 3 or 4 generations of chipsets come out since then.
As it's been said, motherboard RAID is usually about as good, if not worse, than hardware RAID. They are certainly not much faster. However, they are perfectly adequate for someone that wants a simple backup plan and doesn't care much about performance or crazy-level stability.
The only problem is that finding a good hardware RAID controller can be expensive. However, if you're data is that critical to you (or if you just want a FAST RAID 10 array), it's definitely worth the money.
The original proposition was "Onboard Raid VS Software Raid". As it has been said,"buying a RAID card, and installing it in your computer is good", better still buying a GOOD QUALITY Fast Raid card, SCSI or SATA, beats software or onboard in my experience. A myriad of setting determine the performance of your array, from picking the correct slot for the card,stripe size used,to Raid type, just to name a few. Spend the dollars on a good quality hardware option that's compatible with your system and you will not regret it. In my experience, our clients don't mind paying for Quality, we say to them, "How much is your downtime worth to you".
I've made such good experience with software raid, that I'll never buy a hardware raid controller for private use. It's just not worth the money, since my bottle neck is the ethernet card with its 1gbit/s.
I'm using a 2GHz single core with 2GB RAM on a 5x1.5TB software RAID5 and there always comes the gigabit over the network (for a single user). bonnie++ says 160MB write and 250MB read (sequential).
Also my software RAID0 (on 4x500GB, 2G RAM, 2GHz dual core) delivers enough performance for our club's private use: