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Why even use RAID?

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May 15, 2011 11:16:19 PM

So, I just got done setting up my first RAID array: 3 1tb Seagate Barracudas in RAID 5. I've been benchmarking so I can check out the results of my handiwork, and I must say, I'm not impressed with this.

I use my machine for day-to-day web-surfing, audio recording and editing, gaming, content-streaming, media storage, and to drive my LCD TV to watch netflix ;)  . Before I setup this array, I was running everything off of a single Western Digital 500gb HDD that I bought in the days when 500gb was an impressive amount. Going from that to a RAID 5 array, I expected:

1) Vastly increased read/write speeds
2) Noticeably shorter windows load times
3) A smaller system i/o footprint and, thus, snappier response time (esp. during heavy i/o activities)
4) Substantially decreased application load times (and load times in games)

After setting up my array, I benchmarked the performance via the criteria on this page http://www.overclock.net/hard-drives-storage/111116-off... and, tbqh, I'm getting really unimpressive results:

According to ATTO, my single WD HDD is smoking my RAID 5 array in writes by consistently > 2x, and sometimes > 10x!! Reads jump up into 200MB/s range on the Raid5, but I feel like taking the hit in writes isn't worth it.

According to HD Tach:

my single WD HDD
-average read speed: 56MB/s
-random access: 21ms
- burst: 198MB/s

Intel Raid 5 Array:
- average read speed: 61MB/s
- random access: 20ms
- Burst 178MB/s

This is all on an Asus P6T mobo with an intel ICH10R driver. Are these results normal? Am I missing something? Is my ICH10R driver not working? If this is just what's to be expected, I'm taking these HDDs back because this wasn't worth the time, effort, or money. :( 

Thanks everyone!

More about : raid

a b G Storage
May 15, 2011 11:52:04 PM

Well you aren't using hardware raid for a start and RAID 5's primary concern isn't speed; it's capacity whilst maintaining some redundancy.

You should have been using RAID 0 if you were so dead set on performance only.
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May 16, 2011 12:16:10 AM

Rusting In Peace said:
Well you aren't using hardware raid for a start and RAID 5's primary concern isn't speed; it's capacity whilst maintaining some redundancy.

You should have been using RAID 0 if you were so dead set on performance only.


Thanks for replying. Raid 0 is too unsafe, and buting an additional external backup is out of my price range right now.

I've heard that there can be some confusion surrounding wether or not you're using hardware raid. Since this is a setting in bios, I thought that was a good sign that this is hardware raid? Does hardware raid only come from a pci raid controller? I thought the p6t came with a built in raid controller?

So, these results are the best I can hope to get?
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May 16, 2011 12:17:16 AM

Sorry for the typos. I'm responding from my smartphone.
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a c 415 G Storage
May 16, 2011 12:17:52 AM

RAID is right up there with 6Gbit/sec SATA hard drives as one of the most misunderstood technologies. RAID has some very specific benefits and limitations, but most end users don't seem to really understand what they can reasonable expect from them.

RAID-5 has extremely poor write performance because of the way it has to update the parity information whenever a data block changes.

RAID-0 has the best transfer rate performance - it can potentially double the transfer rate when you use two drives if block sizes, stripe sizes and I/O alignment work out just right. But it is also the least reliable organization - you'll loose ALL your data if ANY drive dies.

The thing to remember is that while some RAID organizations can improve transfer rates, NONE of them can improve access times. The time required to boot windows and start applications is more dependent on access times than transfer rates, so don't expect any RAID system to work miracles for those kinds of tasks.

It doesn't matter whether you're using hardware or software RAID - these fundamental limitations still apply.

If you want to improve access times, the only way to do it is to use a drive that is inherently faster - for example the 10,000rpm Velociraptors or 15,000 rpm Enterprise-class hard drives. But an SSD blows everything else right out of the water - it has access times about 100 TIMES faster than a standard hard drive.
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May 16, 2011 5:12:41 AM

sminlal said:
RAID is right up there with 6Gbit/sec SATA hard drives as one of the most misunderstood technologies. RAID has some very specific benefits and limitations, but most end users don't seem to really understand what they can reasonable expect from them.

RAID-5 has extremely poor write performance because of the way it has to update the parity information whenever a data block changes.

RAID-0 has the best transfer rate performance - it can potentially double the transfer rate when you use two drives if block sizes, stripe sizes and I/O alignment work out just right. But it is also the least reliable organization - you'll loose ALL your data if ANY drive dies.

The thing to remember is that while some RAID organizations can improve transfer rates, NONE of them can improve access times. The time required to boot windows and start applications is more dependent on access times than transfer rates, so don't expect any RAID system to work miracles for those kinds of tasks.

It doesn't matter whether you're using hardware or software RAID - these fundamental limitations still apply.

If you want to improve access times, the only way to do it is to use a drive that is inherently faster - for example the 10,000rpm Velociraptors or 15,000 rpm Enterprise-class hard drives. But an SSD blows everything else right out of the water - it has access times about 100 TIMES faster than a standard hard drive.



Thanks so much for this info! I think you're right. I had some misconceptions about this technology. I knew that there was a performance hit associated with going with RAID 5 over RAID 0, I just didn't know that it was a performance hit relative to just having a single drive :heink: 

I thought about just running my OS off of an SSD, but some things bother me about that. First off, I'm going to have to run the SSD for my OS and essential (small) software, a large drive for data storage and non-essential (or large) software, and presumably an even larger drive to back up the other two. That, to me, seems inefficient as all hell. Not only is it inefficient, but communication between the drives will be limited by the presence of the HDDs, and I won't get the performance boost I'm looking for because all data/games will be on the conventional drives anyway. I feel like I would be paying X amount of dollars to have Windows start up REAAAALLY fast - which is cool and all, but probably not the best use of my resources. :lol: 

I could run a RAID array for the data disks, but then i'm back here again. I dunno.
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May 16, 2011 5:32:57 AM

or just run raid 1+0+0 aka raid 100 XD
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May 16, 2011 5:35:02 AM

If your board supports raid 0+1 you could go with that particular setup which mirrors a set of striped disks or stripes a set of mirrored disks there are both types, this gives you redundancy and speed with no parity calculation so it should give you your speed boost with less risk.

A quick search shows that at least one asus board with this chipset supports raid 10 so take a look, you can do this with either hdds or ssds but since you already have 4 hdds simply set this up and try it out.

I personally use 2 ocz 60gig agility 2 drives in a striped array with write cache.
Crazy performance check it out http://i878.photobucket.com/albums/ab341/soloreaper/dis...

I have all my alternate games installed on a striped normal 1tb i get about 200mb sustainable from those.
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May 16, 2011 5:37:07 AM

Yeah, I was just looking into doing that. Problem is that my 4th drive is only 500gb. Can you do an efficient RAID 1 + 0 with 3 1tb and 1 500gb?
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May 16, 2011 5:57:24 AM

Ok, so an interesting development has transpired. Apparently I didn't have the "intel rapid storage" driver installed. It's not for want of trying though. Why is it so damn hard to get drivers installed without doing it in the process of installing the OS?? I'm not even sure I have the proper ich10r driver installed...or if it's even installed at all! My ASUS CD only allows you to create a driver install disk via the floppy A drive...which i haven't had in years.

Anyway, now that at least one of the drivers I need has been installed, my RAID 5 read speeds are off the charts on ATTO as well as HD Tach. However, according to ATTO, my write speeds are generally < 1 meg until the 16 test. After that it's a slow ramp up to 9meg write speeds. :\

Atto:
Read Speeds stay around +240mb/s @ 4.0 - 1024 tests
Write speeds never get above 10 meg :( 

HD Tach:
Burst: 2,758/mb/s :D 
Random Access: 14.6ms
Average Read: 201 mb/s
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