2x RAID5 vs 1x RAID10

[jstraten]

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

[golddiggie]

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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[RParker]

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.

[RParker]

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.

[jstraten]

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!

[a_p_]

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

[jstraten]

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.

[RParker]

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.

[golddiggie]

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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[RParker]

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.

[jstraten]

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

</div>

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!

[golddiggie]

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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[jstraten]

|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.

[RParker]

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.

[golddiggie]

|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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[a_p_]

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

[RParker · Accepted solution]

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.

[jstraten]

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.

[RParker]

Can I build a RAID50 with six drives?

That's the minimum requirement, 6 drives.

[jstraten]

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.

VMware VCP4

Consider awarding points for "helpful" and/or "correct" answers.

</div>

Could you elaborate on the purpose of the battery?

Thanks!