In my system I can either way have two RAID5 arrays or one RAID10 array. Now, my questions are:
1. What is the better option for a VMware ESXi environment?
2. What gives me better performance? I mean I do understand that RAID10 writing is faster than RAID5, but is this statement still true if I am writing against two different RAID5 arrays?
3. How about data safety? From what I can see there are no differences between RAID5 and RAID10. Is that correct?
Thanks,
Jens
So, I am still wondering: Are two RAID5 faster than one RAID5?
Probably but only marginally and only IF you have 2 separate controllers. If you put 2 RAID 5 on the controller that means that one controller controls BOTH RAID groups. So for this it would be slower, if you can stick 2 RAID controllers each managing the RAID 5 separately it might be a little faster, but I doubt it. 2 RAID 5 means that EACH array is still a RAID 5, RAID 10 is the fastest you can get, period (other than RAID 0). This assumes the same number of spindles.
RAID 5 with 6 spindles, 2 RAID 5 with 3 spindles each, or a RAID 10 on 6 spindles. RAID 10 beats RAID 5, RAID 50.
How many spindles are you looking to use? How about going best of both worlds with RAID 50 (http://www.acnc.com/04_01_50.html)? Is your system listed on the HCL? What RAID controller are you using?
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1. What is the better option for a VMware ESXi environment?
It's apples vs pomegranates.
RAID 5 is only 1 parity stripped, but you lost N-1 disks. RAID 10 is better performance but you lose HALF of all the drives in the Array (thus only 50% space available), so it's a trade off.
I would think RAID 5 is slightly better security, RAID 6 even more still. READS are better on RAID 10 writes are better on RAID 5.
RAID 50
While this may be true, most internal RAID cards don't support RAID 50, only option is RAID 0,1,10, 5 and 6.
This is for a development environment.
Hardware:
- System is SuperMicro 6026T-NTR+ which is listed on the HCL
- RAID Controller is Adaptec 5805 with 6 x 2TB and 1 x 1TB (For ESXi & ISO images)
- 32GB RAM
We plan to install 3 VMs on this system. One of the VMs will only be used infrequently (once a month). The other two would be on 24x7.
I am just wondering if two RAID5s would perform better (write & read) than one RAID10 in this scenario. Is the total performance by controller or by disk array? Do two disk arrays work in parallel or do they work sequential?
Thanks!
RAID10 might be the fastest RAID level to choose, however with RAID5 (with the 6 disks you mentioned in the other thread) I assume you won't see much difference in performance since there are enough disks on which the controller can write simultaneously.
In both RAID levels you can loose 1 disk. (On RAID10 you could actually loose 3 disks. Depends which ones.)
There is a huge difference in available disk size. With RAID10 you will have 6TB, with RAID5 it's 10TB.
So what I would recommend for your system is a RAID5 with 5 disks and 1 hot spare. This way you have more safety and also 8TB of disk space.
Make sure to add a battery cache to your Adaptec controller, this makes a very big difference in disk performance.
Also be aware that the max. VMFS size for 1 LUN is 2TB - 512 Bytes when using 8MB block size.
André
1. What is the better option for a VMware ESXi environment?It's apples vs pomegranates.
RAID 5 is only 1 parity stripped, but you lost N-1 disks. RAID 10 is better performance but you lose HALF of all the drives in the Array (thus only 50% space available), so it's a trade off.
I would think RAID 5 is slightly better security, RAID 6 even more still. READS are better on RAID 10 writes are better on RAID 5.
50% space loss is acceptable to us if the performance would be significantly better (especially write performance).
Hmm, I thought this to be other way round. Doesn't RAID 10 have faster write performance than RAID 5?
Or, are you referring to two RAID 5 writing faster than one RAID 10 (which is basically my question).
Thanks.
RAID Level | Total array capacity | Fault tolerance | Read speed | Write speed |
RAID-10 500GB x 4 disks | 1000 GB | 1 disk | 4X | 2X |
RAID-5 500GB x 3 disks | 1000 GB | 1 disk | 2X | Speed of a RAID 5 depends upon the controller implementation |
You can clearly see RAID 10 outperforms RAID 5 at fraction of cost in
terms of read and write operations.
jstraten wrote:
RAID Controller is Adaptec 5805 with 6 x 2TB and 1 x 1TB (For ESXi & ISO images
http://www.adaptec.com/en-US/products/Controllers/Hardware/sas/performance/SAS-5805/
Supports RAID levels: 0, 1, 1E, 5, 5EE, 6, 10, 50, 60
Make sure you get the battery with/for the controller too. It's listed as an optional item.
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So what I would recommend for your system is a RAID5 with 5 disks and 1 hot spare. This way you have more safety and also 8TB of disk space.
What is the purpose of a spare? You can lose a disk in RAID 5 and the RAID will still function, the big difference there is you LOSE that spare permanently just by making it a "hot" standby. I would rather have the performance than waste 500 bucks on something taking up energy.
For that matter just make it a RAID 6 and be done with it. The RAID 5 vs RAID 6 is minor difference in speed.
RAID10 might be the fastest RAID level to choose, however with RAID5 (with the 6 disks you mentioned in the other thread) I assume you won't see much difference in performance since there are enough disks on which the controller can write simultaneously.
In both RAID levels you can loose 1 disk. (On RAID10 you could actually loose 3 disks. Depends which ones.)
There is a huge difference in available disk size. With RAID10 you will have 6TB, with RAID5 it's 10TB.
So what I would recommend for your system is a RAID5 with 5 disks and 1 hot spare. This way you have more safety and also 8TB of disk space.
Make sure to add a battery cache to your Adaptec controller, this makes a very big difference in disk performance.
Also be aware that the max. VMFS size for 1 LUN is 2TB - 512 Bytes when using 8MB block size.
André
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If I understand you correctly, you are recommending one RAID5 with 1 hot spare. Is that basically RAID6?
So, I am still wondering: Are two RAID5 faster than one RAID5?
I guess I am uncertain about the controller capabilities. I mean is it smart enough to read/write disks in one RAID array at the same speed as it would in two arrays? This is probably a trivial question, but I am pretty new to RAID hardware.
Thanks!
With the controller you're listing, you could do 8 1TB SAS drives in a RAID 50 array, have the space of six of them and be in a good position for speed and parity. I wouldn't give the boot/ISO virtual drive 1TB, you could easily go with 200GB or less there without issue. Use the remaining space to make your LUNs 2TB-512B in size, giving the balance for a final LUN and be good to go.
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|RAID Level|Total array capacity|Fault tolerance|Read speed|Write speed|
RAID-10 500GB x 4 disks | 1000 GB | 1 disk | 4X | 2X |
RAID-5 500GB x 3 disks | 1000 GB | 1 disk | 2X | Speed of a RAID 5 depends upon the controller implementation |
You can clearly see RAID 10 outperforms RAID 5 at fraction of cost in
terms of read and write operations.
</div>
I have seen this chart before. However, I am still wondering if this is still true if you compate TWO RAID 5 arrays with ONE RAID 10 array.
I have seen this chart before. However, I am still wondering if this is still true if you compate TWO RAID 5 arrays with ONE RAID 10 array.
It's clear you are hell bent on using RAID 5. So use RAID 5 then.
|RAID Level|Total array capacity|Fault tolerance|Read speed|Write speed|
RAID-10
500GB x 4 disks
1000 GB
1 disk
4X
2X
RAID-5
500GB x 3 disks
1000 GB
1 disk
2X
Speed of a RAID 5 depends upon the controller implementation
You can clearly see RAID 10 outperforms RAID 5 at fraction of cost in
terms of read and write operations.
</div>
I have seen this chart before. However, I am still wondering if this is still true if you compate TWO RAID 5 arrays with ONE RAID 10 array.
</div>Only if you're talking about striping the two arrays... AKA RAID 50...
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RAID5 with hot spare is not really the same as RAID6.
The difference is, RAID5 is a little bit faster, however when you loose a disk the stand by disk has to be rebuilt. On RAID6 all disks are in use (2 parity disks) and you can loose two disks.
A RAID5 with 3 disks is the slowest configuration you can choose. On RAID5 each write has to lock 2 disks (data and parity), so only one write at a time can be done.
André
So, I am still wondering: Are two RAID5 faster than one RAID5?
Probably but only marginally and only IF you have 2 separate controllers. If you put 2 RAID 5 on the controller that means that one controller controls BOTH RAID groups. So for this it would be slower, if you can stick 2 RAID controllers each managing the RAID 5 separately it might be a little faster, but I doubt it. 2 RAID 5 means that EACH array is still a RAID 5, RAID 10 is the fastest you can get, period (other than RAID 0). This assumes the same number of spindles.
RAID 5 with 6 spindles, 2 RAID 5 with 3 spindles each, or a RAID 10 on 6 spindles. RAID 10 beats RAID 5, RAID 50.
With the controller you're listing, you could do 8 1TB SAS drives in a RAID 50 array, have the space of six of them and be in a good position for speed and parity. I wouldn't give the boot/ISO virtual drive 1TB, you could easily go with 200GB or less there without issue. Use the remaining space to make your LUNs 2TB-512B in size, giving the balance for a final LUN and be good to go.
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</div>
I am more and more considering RAID50 now. It seems that it somehow meets most of my requirements in regards of performance, parity and space loss. Can I build a RAID50 with six drives? My server only has 8 slots.
I hear you about the 1TB being wasted. I think I will have to redo that drive and follow your suggestion to create two RAID 0 LUNs against that drive.
Can I build a RAID50 with six drives?
That's the minimum requirement, 6 drives.
jstraten wrote:
RAID Controller is Adaptec 5805 with 6 x 2TB and 1 x 1TB (For ESXi & ISO images
Supports RAID levels: 0, 1, 1E, 5, 5EE, 6, 10, 50, 60
Make sure you get the battery with/for the controller too. It's listed as an optional item.
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Consider awarding points for "helpful" and/or "correct" answers.
</div>
Could you elaborate on the purpose of the battery?
Thanks!