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Very slow Raid 5 - why?

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February 16, 2009 5:29:59 PM

Hi;
I've been following the Raid 5 thread with much interest. I have configured an internal Raid 5 with 4 Seagate 500gb SATA II drives. So far, it has gone down twice by what I believe to be a combination of bad data writing and then informing me on boot-up that I need to run CHECKDISK, which I have learned that you should never run on a RAID. I have a very fast quadcore processor, good motherboard and am running XP-64bit....I use the computer for Video editing, and was under the impression that RAID 5 was the way to go in terms of safety, so as not to lose a project. After reading what has been posted, I'm just wondering if the write errors are being generated by the digitizing of video. The RAID has never told me that it wants to rebuild itself due to errors, and I always believed that this was part of the advantage to RAID 5.

I'm using a RocketRaid 2310 controller card, and while their tech support has been enthusiastic, they have not been that helpful, and I'm re-initializing and trying to rebuild it for the 3rd time. I'm really hoping that someone has some experience with video or large files that require fast read/write times. Also, a way to check both the thruput speed of the RAID and/or the validity of the data on the drive would be very useful.

This thread has really been an education for me, and goes beyond what many of the writers in the video mags and blogs (where I have learned most of what I know about this) have to say, and I really appreciate it. I would also appreciate any opinions about my particular issues and any suggestions.

Thanks very much.
Richard Berger
divaproductions@gmail.com

More about : slow raid

February 16, 2009 8:36:17 PM

Hi Richard,

You are using a software enabled RAID controller. You might as well be using SW RAID that comes with some motherboards. You should be using a HW RAID controller which will cost you some where from 200-700$. This will offload all of the XOR function to the controller and not waste CPU resources.

Good Luck,
Gatorbait
February 16, 2009 11:23:09 PM

Hi Gatorbait

Thanks for the reply. The RocketRaid 2310 is a 4 port PCIe hardware controller. Not the most expensive, but well reviewed.

R...


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February 17, 2009 12:46:42 AM

Sorry HarryOOO but gatorbait is correct. The Highpoint series does have an XOR processor onboard until the 3xxx series. Yes the 2310 has some high functions than the current onboard controllers but it still offloads calculations to the CPU.

Although its a not a fully fledged hardware controller you shouldnt have dropouts happening of this nature. Are you sure the 4 HDDs are in correct working order you could try running scans on all the drives if your able to. All the cables are in working order. Check the options for the array in the BIOS of the controller, it maybe an issue with Cache writing or block sizes. Is there a firmware upgrade for the controller?
February 18, 2009 3:57:26 PM

Hi Chookman;

Not exactly sure what an XOR processor is, and I wasn't aware that it offloaded calculations to the CPU. They don't tell you that in their sales pitch...I've reconfigured the RAID as a RAID 0, and will see how it performs. I've been trying to find a piece of software that will allow me to test all the drives in a RAID configuration...maybe you know of something that will do this job? Cables all good, etc. I have it set for write-back and blocks of 512k, which seems to be the standard.
Anyway, what's an XOR processor and is there some software you know of that will test the thing?

Thanks so much,

R...


February 19, 2009 12:41:15 AM

Exclusive or http://en.wikipedia.org/wiki/Exclusive_or

Basically the processor that does the calculations for the array (parity, etc.)

You'll notice as i said on the 3xxx from Highpoint in the specifications they list an Intel Processor (i haven't seen any other than Intel designed), without one these calculations will be done on the CPU (no biggie really)

I dont know of any software that you can test the drives with while the array is in working order, the majority of software from the vendor should be enough to detect any problems with the disks. Have you checked for a firmware update on the controller?
February 19, 2009 7:51:00 AM

There is no reason not to run CHKDSK on a RAID array! You may be rebuilding without good reason. Run Memtest86 to make sure you don't have int memory fault. RAID 5 should ID the problem drive and give option to rebuild the array. If more than one drive has problem, test the drives one at a time with Seatools. If they pass i would get the RAID card changed as faulty.

Mike.
February 19, 2009 5:58:50 PM

I'm curious about this. Does software RAID really make enough of a hit on a quad core's performance to justify spending an $200+ on a hardware RAID card?...or are hardware RAID cards just $200+ faster?
February 20, 2009 12:29:30 AM

Halcyon, That is an excellent question.
The answer really depends several factors:
1) Is the software raid a dedicated RAID application or engine on a single core?
2) What is the architecture of the CPU and/or memory controller. Is there shared memory with one or more cores running applications. Is there a single bus to a Memory controller for all cores to share. Etc.
3) Does the Dedicated HW RAID card Have memory battery backup so it can be configured in write back vs. write thru?
4) How well is the software RAID integrated within the OS or multiple OS arrangement? Priority of internal CPU buses via the software.
5) During a re-build or migration, how much of a BUS capacity will be utilized by the SW RAID? Will that impact other Applications trying to use other IO ports?
6) For SW RAID, will you be using the south bridge drive ports, or will you be using a dedicated drive controller that has some additional cost, but adds flexibility?

Overall, the HW RAID controller will give you excellent performance without the headache of making sure your Server/OS/APPS/SW RAID is architecturally set up perfectly.
February 20, 2009 9:17:35 AM

Thanks Gatorbait for the reply, good information worth saving.
February 20, 2009 6:52:06 PM

This is something to think about. I have the Highpoint 1540 4 port controller card on an Nforce4 motherboard. I would constantly get broken raid5 array errors on startup. But within Windows everthing seemed ok, array capacity was intact. Another issue I would get is the "Delayed write failed" error. I tried all sorts of drivers till I came across Fernando's modified drivers at Nforcershq. His latest nf4 non-ahci driver has worked wonders for me. No more errors of any kind with the 1540 or the 2310. One clarification, I got the 2310 after the working driver so I can't verify that there were errors with nvidia's stock driver. On a side note, the 2310 card is much faster in raid0. Raid5 on both Highpoint cards, 1540 and 2310, is about the same 25-30mb reads using HDTune. I hope this helps.
February 20, 2009 9:31:16 PM

Very helpful for me. Since I reconfigured my RAID 5 to RAID 0, I have not had a problem. I think video might be less complex than some of the issues discussed here, altho the file sizes are very big (particularly hi-def video). I'm most interested in a big, fast flowing pipe (throughput), and read/write speed...and I think I'm just going to stick to RAID 0...it works. I'll deal with a backup system in some other way.

Configured as RAID 0, the Highpoint 2310 seems rock solid, and far superior to the first thing I tried with this machine, which was on the motherboard...and the machine seemed a little slow. Now, it screams.

Q9550 processor
Gigabyte MB
4 GB DDR 3 Ram

Thanks everyone who posted...I really appreciate it...

R...
February 20, 2009 10:11:38 PM

Just to give you and idea, with 4 x 60GB laptop drives in raid0 the read transfer graph is slightly choppy but pretty flat and an average of 84.4MB/sec 3.9% cpu usage. Write transfer averages 25.8MB/sec 3.6% cpu usage. The graph is much choppier and transfer rate decreases as it gets to the end of the array. Writes seem disproportionately low. I haven't tried with other hard drives yet.
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