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Old 10-06-2012, 22:51   #1
CitizenOfDreams
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RAID5 suxx

So, I bought three 3TB drives and made a RAID5 with them, despite numerous advices against it (there is even a society called BAARF - Battle Against Any RAID Four/Five).

But, of course, I just had to see it for myself...

With the "fake" onboard RAID controller (Intel ICH10R), I did not expect any stellar results. But the reality was even worse than I expected.

First of all, it took two days to initialize the RAID. You can use the arrays before and during initialization, but the performance would be really abysmal. So what did I get after the long wait was over?

Sequential read speed: down 27% compared to a standalone disk.
Sequential write speed: down 44%.
512K block read speed: down 32%.
512K block write speed: down 88%. Ouch.
4K block read speed: up 4%. Probably just a statistical deviation.
4K block write speed: down 12%.
4K block read with queue depth 32: up 125%.
4K block write with queue depth 32: down 8%.

I think I should go buy one more drive and make a RAID10.
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Old 10-07-2012, 16:23   #2
srhoades
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If you want true RAID performance they you need to buy a real RAID card. They start around $300. You can't discount RAID based on an onboard controller.
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Old 10-07-2012, 16:38   #3
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interesting. I didn't think anyone actually used onboard controllers anymore. Ditch that setup and try mdadm. Aside from one weird conflict with time machine, mine (raid 6) seems to run pretty fast. . it would be interesting of you could compare results.
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Old 10-07-2012, 17:13   #4
CitizenOfDreams
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It's just a home computer, not an enterprise server. All I need is more capacity, a little more speed, and some fault tolerance compared to a single drive (which most home computers use).

The onboard controller is perfectly adequate for my needs. It doesn't work well with RAID5, but "real" controllers don't do RAID5 too well either. They just mask its inherent problems with a large cache.
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Old 10-07-2012, 17:32   #5
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Of my 13 servers 11 of them run raid 5 with no problems. They are a mix of ultra 320 SCSI and sas and both run great. My 2 database servers run raid 10. Remember each raid level has a purpose. If you are looking for max write performance raid 5 is not the way to go read speed is good with raid 5 with a real controller.

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Old 10-07-2012, 19:21   #6
sappy13
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I run raid 5 for all of my clients servers. Haven't had a single performance issue yet. Get a quality raid card and u will have good results.

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Old 10-14-2012, 11:35   #7
CitizenOfDreams
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Update...

I put together a 4-disk RAID10. I'm very happy with its performance, just noticed one strange thing: enabling write-back cache drastically decreases the write speed with 512K block size. Sequential write speed and 4K write speed are not affected.

Here are the benchmark results (with WB disabled):

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Old 10-14-2012, 14:38   #8
tcruse
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The Intel RAID controller on the motherboard does not perform very well on any raid level. Also, you need to buy drives tat are certified for raid use, (at least 7300 rpm and lot f memory buffer n drive) otherwise soft errors will cause you to always be in recovery mode.
The sub $200 large drives do not do well, also avoid the "green" drives.
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Old 10-14-2012, 16:08   #9
CitizenOfDreams
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Quote:
Originally Posted by tcruse View Post
The Intel RAID controller on the motherboard does not perform very well on any raid level.
It still performs better than a single drive, while providing some degree of fault tolerance. That's all I need and that's all I care to pay for.

Quote:
Also, you need to buy drives tat are certified for raid use, (at least 7300 rpm and lot f memory buffer n drive) otherwise soft errors will cause you to always be in recovery mode.
Seagate Barracuda, 7200RPM, 64MB cache, $150. Haven't seen any warnings yet, the RAID stays in one piece. We'll see how it goes.

One thing to note: you absolutely need good cooling when you stack several hard drives in one case. I have a fan on each drive; without the fans running the temperature jumps up from 35C to 50C.

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