RAID 10 vs RAID 5, a good example

CoryS

Ok this write up is based on older disks but the perfomance difference is staggering. I have been doing alot of capacity planning so this was nice to finally see some graphs and actual benchmarks side by side.. I would be curious to see these same benchmarks using the newest SAS 15k drives vs the 10k drives...

Anyway, for what its worth... (The default Windows block size is still 64K)
http://www.alliancesystems.com/Documents/RAID10.pdf

Have a good day.

Mishra

From personal views on the performance difference I really don't see that it does that much. If you are thinking about 30 disks then with RAID 10 you will actually see a good difference but if you only have 15 or under then it really is whether or not you can afford to lose the space or not.

HeroPsycho

As an Exchange expert, I'm gonna disagree. It really depends upon the application. Rapid read/write applications like Exchange benefit significantly from RAID10 over RAID5.

Know your apps, and what they run best with.

royal

HeroPsycho wrote:

As an Exchange expert, I'm gonna disagree. It really depends upon the application. Rapid read/write applications like Exchange benefit significantly from RAID10 over RAID5.

Know your apps, and what they run best with.

Agreed

Mishra

HeroPsycho wrote:

As an Exchange expert, I'm gonna disagree. It really depends upon the application. Rapid read/write applications like Exchange benefit significantly from RAID10 over RAID5.

Know your apps, and what they run best with.

I did my benchmarking on Exchange and was able to test load under RAID 5 and RAID 10. It was just fact that when you only have 15 disks or lower the difference really isn't that much.

HeroPsycho

I worked for Microsoft Premier Product Support for the Exchange Admin team, and did a lot of performance optimization and troubleshooting. Absolutely without a doubt RAID10 has a clear distinct advantage in performance over RAID5 even with less than 15 disks in most configurations. You might not have seen it, but believe me, and no offense, I guarantee you I've seen more environments, and so has the Microsoft Exchange team, hence why they recommend RAID10 over RAID5 without a minimum number of disks disclaimer.

Not trying to flame or anything, but sharing my experiences...

Mishra

HeroPsycho wrote:

I worked for Microsoft Premier Product Support for the Exchange Admin team, and did a lot of performance optimization and troubleshooting. Absolutely without a doubt RAID10 has a clear distinct advantage in performance over RAID5 even with less than 15 disks in most configurations. You might not have seen it, but believe me, and no offense, I guarantee you I've seen more environments, and so has the Microsoft Exchange team, hence why they recommend RAID10 over RAID5 without a minimum number of disks disclaimer.

Not trying to flame or anything, but sharing my experiences...

I didn't say that there wasn't a clear advantage, yes there IS a performance increase. All I'm saying is if you have a small environment and you configured your exchange platform in a RAID 5 I wouldn't really sweat the fact that you didn't RAID 10 your disks. I wouldn't try to re-engineer my exchange environment to try and get a RAID 10 for the bit of performance you will save. You don't agree with that?

HeroPsycho

Mishra wrote:

[If you are thinking about 30 disks then with RAID 10 you will actually see a good difference but if you only have 15 or under then it really is whether or not you can afford to lose the space or not...

I didn't say that there wasn't a clear advantage, yes there IS a performance increase. All I'm saying is if you have a small environment and you configured your exchange platform in a RAID 5 I wouldn't really sweat the fact that you didn't RAID 10 your disks. I wouldn't try to re-engineer my exchange environment to try and get a RAID 10 for the bit of performance you will save. You don't agree with that?

First off, if you look above, you did imply there isn't a clear advantage with RAID10 if you have 15 disks or less. I'm not twisting your words around here.

And secondly, no, I don't agree with it. The size of your environment has nothing to do with it. It's simply a matter of what IOPS you need now and in the future vs. how much storage space you need vs. your budget. Of you have 500 users on the Exchange server instead of 2000, if those one 500 users don't use cached mode or there is heavy delegate mailbox access, and users don't keep the number of items in their critical paths folders down, then RAID10 without a doubt should be used because you would more likely see disk performance issues.

If you don't need the IOPS, you don't need the IOPS.

And I'm going to point out that you apparently judged the relative performance of RAID10 vs. RAID5 by Outlook/client experience. How do you know if the bottlenecking of your Exchange environment wasn't processor, lack of RAM, not having the proper performance tuning settings in place, etc.? Was your client in cached mode? If so, then your local machine was doing the heavy IO work most of the time. If it performed just as well either way by a subjective view of Outlook experience, how could you then objectively compare RAID10 vs. RAID5? Simple answer: you can't.

You should have done IOPS calculations using tools like IOMeter, Jetstress, etc.

No one said anything about what you should do once Exchange is deployed. That is a completely entire different can of worms. Re-engineering is absolutely in order if there's a storage performance problem that you can correct switching to RAID10.

Again, I'm sticking to my statement that you need to know your application and its disk performance needs before you can intelligently choose your RAID level.

Mishra

Terrible response. I'm trying to figure out what your angle is and you are putting words in my mouth.

Thanks.

snadam

Mishra wrote:

Terrible response. I'm trying to figure out what your angle is and you are putting words in my mouth.

Thanks.

Mishra, im not trying to be an ass here....but

Mishra wrote:

I did my benchmarking on Exchange and was able to test load under RAID 5 and RAID 10. It was just fact that when you only have 15 disks or lower the difference really isn't that much.

AND

Mishra wrote:

From personal views on the performance difference I really don't see that it does that much. If you are thinking about 30 disks then with RAID 10 you will actually see a good difference but if you only have 15 or under then it really is whether or not you can afford to lose the space or not.

call me crazy, but I don't think heropsycho is putting words in anybody's mouth.

Mishra

snadam, I was trying to be done with this conversation after hero's post but I don't mind explaining what I see as long as we remain civil. I'm not trying to attack anyone here. It is just a post on the internet and I was just trying to give level headed opinions.


Yes, I said that there isn't much of a difference. So that means that there is a difference, and that being RAID 10 has more performance. Thus I'm trying to avoid anyone thinking that I'm trying to say there is NO difference. But, again, the difference really isn't as great as articles might elude to.

But after I gave a quick opinion and didn't even explain how I came to that conclusion, and I get someone saying stuff like

"I'm not twisting your words around here. "
"you apparently judged the relative performance of RAID10 vs. RAID5 by Outlook/client experience."
"If it performed just as well either way by a subjective view of Outlook experience, how could you then objectively compare RAID10 vs. RAID5? Simple answer: you can't.
"

Then obvious he thinks that I don't know what I'm talking about and he just assumes I'm an idiot. Especially with ego waving like

"I worked for Microsoft Premier Product Support for the Exchange Admin team"
"I guarantee you I've seen more environments, and so has the Microsoft Exchange team"

even though he has no idea where I work or what I've done.

It is just a pointless conversation right?

If more people would try to explain things like "In my experiences, I've seen.... and I think that because..." then it would be a lot easier to have a civil conversation instead of saying "I've seen more environments than you and you are wrong. I bet you didn't do... and I bet you are stupid and doing..." which just makes it hard not to be offended.

cisco_trooper

Holy crap, dude...

Mishra

cisco_trooper wrote:

Holy crap, dude...

lol too picky for you?

HeroPsycho

Thank you for the kind words, snadam...

Mishra wrote:

Then obvious he thinks that I don't know what I'm talking about and he just assumes I'm an idiot. Especially with ego waving like

"I worked for Microsoft Premier Product Support for the Exchange Admin team"
"I guarantee you I've seen more environments, and so has the Microsoft Exchange team" even though he has no idea where I work or what I've done.

I'm sorry I said Microsoft is more experienced and knows more about this than you do. FYI, storage vendors such as EMC also say the same thing. But you're right, I don't know what your experiences are, so you maybe you do know more than the likes of Microsoft and EMC.

For the record, I don't think you're an idiot. I simply think you're mistaken about this topic.

dynamik

What's with all the commotion fellas?

I think the point Mishra was trying to make is that in small organizations where RAID-5 provides an acceptable level of performance, a switch to RAID-10 for a negligible performance increase wouldn't be worth the time and/or money. I believe that's a fair statement.

While HP (who is clearly quite knowledgeable) could have certainly used a little more tact, I don't think anything he said was intended to be a personal attack. This really isn't something that's worth getting worked up over.

We really need this writers' strike to end, so we can do something else besides bicker over RAID

cisco_trooper

Amen to that brother...