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RAID Problems With Intel Core 2?
Nom du Keyboard writes "The Inquirer is reporting that the new Intel Core 2 processors Woodcrest and Conroe are suffering badly when running RAID 5 disk arrays, even when using non-Intel controllers. Can Intel afford to make a misstep now with even in the small subset of users running RAID 5 systems?" From the article: "The performance in benchmarks is there, but the performance in real world isn't. While synthetic benchmarks will do the thing and show RAID5-worthy results, CPU utilization will go through the roof no matter what CPU is used, and the hiccups will occur every now and then. It remains to be seen whether this can be fixed via BIOS or micro-code update."
Yes, i tought about this too.
Using RAID5 in software (be it completely in software like Linux MD or Windows Dynamics Disks, or 99% in Software, like most Onboard RAID Controllers out there) isn't a good idea if you want to run an "enterprise" setup. It might be okay for your mom's basement, or for test systems.
But productive systems should be using real raid controllers, equipped with half a gig of cache memory, a battery backup in case of a power failure for the cache, and dedicated processor for the raid5 overhead.
Intel might've screwed this up, but it will only affect non-professional IT.
I totally agree. If this is actually a RAID-5 setup, then it requires at minimum 3 drives. Most onboard (intel) RAID controllers are only setup for 0,1,0+1, or 10. And not RAID 5. I don't see how it could possibly be correlated to the CPU. It seems much more likely that if it is a new North/South bridge, that the problem is the with IO controller.
CPU utilization in RAID5 configurations is almost entirely offloaded to the RAID controller.
The article (including spelling errors) fails to mention a lick about the RAID controller. Only that "it's a cpu problem."
Software RAID is faster and more reliable than hardware RAID. Should your non-RAID controller fail, you just chuck it and get a random new one. If your RAID-controller fails, you have to get another controller exactly the same, sometimes even the same firmware revision, or kiss your data goodbye. And RAID-controllers are notoriously underpowered (SmartArray, I'm looking at you!)
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Remember that all a HW raid controller is, is a low end (compared to Xeons, etc) embedded CPU running software not unlike what your software raid solution would run.
This extra coprocessor for RAID is great when you have a box doing many different things like rendering, etc. But on a dedicated fileserver you'll be better off using the really fast CPU rather than the much slower raid controller chip to do the RAID logic.
Because it's often slower to do so. We ran tests on a good Adaptec u320 raid controler about a year back and though cpu usage was good. We got much better performance out of Linux softraid5. I would suspect this was because the host cpu was faster than that on the controler.
Not to mention there is a huge cost savings in going with a softraid solution.
Software is more reliable+performance, what are you smoking? To get the performance you've got to turn on write caching, system goes down with write caching you're very likely (almost guaranteed) to have a corrupt filesystem. To get the reliability you turn off write caching, and performance plumments. Any hardware raid worth more than 3 cents has battery backed cache that allows you to have write caching and maintain reliability, not even taking in account being able to do some Raid5 operations with only 1 disk iop.
K6. As a bonus answer... Comparable Intel Processors at the time also had the Microcode Upgrade ability as well.
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You use XOR to clear a register. XOR CX, CX sets the CX register to 0. It is faster than MOV CX, 0.
Professional IT doesn't work like that. You have a maintenance contract on your machine, usually from the machine manefacturer itself (like IBM, HP, DELL, whatever floats your boat). You buy this maintenance contract depending on the time you will need the machine (they're usually available from 3-5 years).
You renew the machine before the contract runs out. IBM, HP, DELL running out of Business seems very unlikely to me.
"3ware card for a few hundred bucks "
The nice 3ware cards for 100 bucks are NOT hardware raid, they use the CPU to calculate the RAID, it might even say it is in the literature but working at company (tech support) who sells servers that use 3ware for 80% of it's business, I can definitely tell you this isn't the case.
You CAN get a hardware based 3ware card, but then you are looking at 400-500 bucks (+some for the battery backup unit).
Plus if you read the parent correctly, 4 300GB hard drives for 50 bucks totals 200 bucks, a "3ware card for a few hundred bucks " WOULD double the cost.
I've never heard it called FAKERAID maybe it should just be called FAID? I'll file that one back for use later...
Anyway, it's not entirely a hw/sw combo. These types of raid controllers are entirely software based. They consist basically of an ata or sata controller and an interrupt handler. When the disk is being accessed in legacy bios mode (ie during an os install, etc) the cpu pulls the interrupt to write to the disk and the BIOS calls the software stored on the card. This software is executed by the BIOS on the CPU and this code basically does whatever reading or writing to disk is necessary to keep the array consistent. Performance is improved after an OS's native driver is loaded since the software raid is done entirely in the driver.
It is arguable that software raid done at the OS level actually can have a performance advantage since it can know about file tasks at a much higher level than the driver itself, which basically only knows about block accesses. In the example presented in the article it seems that most of the tricks that software raid has been using do not perform well on the Core2 chips; I don't really see what the big deal is though; nobody has had a chance to write optimized routines for Core2. Probably their legacy BIOS handling ability is poor; so be it. There are a lot of alternatives out there from completely managing the array inside of software to full on ASIC-based hardware RAID.
In the real world, Core 2 has a comparable or lower thermal envelope than AMD's chips.
No, no, no, no. The processing overhead of parity calculations is miniscule on any remotely modern CPU (even a paltry 300Mhz Pentium 2 has a parity throughput of ~700M/sec).
The performance killer on parity-based RAID configuration is the additional disk reads required to calculate the parity, *not* the parity calculations themselves. Which is why modern software RAID is typically faster than hardware RAID until you get into larges numbers of disks and/or machines with limited bus bandwidth.
This "RAID 5 is slow because of parity calculations" meme must die (although, admittedly, it's a good indicator of whether or not someone really understands what's going on).
These 3ware cards are definitely hardware RAID. You are spreading FUD.
The parallel card is the $110 on newegg.
From Newegg StorSwitch switched architecture delivers the full performance benefit of Parallel ATA's pointto- point architecture up to 133MB/sec per port On-board processor provides true hardware-based RAID and intelligent drive management functions BIOS set up utility and 3ware Disk Management (3DM) web-based management software Bootable array support for greater system fault tolerance
http://3ware.com/products/parallel_ata.asp
That's why we have UPSes. It doesn't matter if your RAID controller has battery-backed write cache if the power to the drives dies.
... And so it comes to this.