Best Disk Array setup for VMware on HP ML350 G6 Server

Posted on 2011-10-22
Medium Priority
Last Modified: 2012-06-21
Hello Folks,

I need to upgrade my client's HP ML350 G6 server's disk array to increase performance and allow for 4th server. The server is running ESXI 4.1. Currently there are 4 146GB drives installed in a RAID5 configuration which we did orginally to meet a budget. I am thinking of adding 4 additional drives, creating a RAID10 array, and moving the more resource demanding servers (such as the SQL server) over to that array to increase performance.

I would like your feedback. Is my above strategy the best way to go about this or is there a better option? My goal is the maximum amount of IOPS I can get from the disk arrays.

Thank You,


Question by:JohnnyD74
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Expert Comment

ID: 37011954
LVL 125
ID: 37011964
Maximum Performance will be obtained by using RAID 10, more disks = more spindles = more performance.

Personally, if you want to max out the performance, re-create the ENTIRE array with ALL the disks in the chassis with RAID 10.

Also ensure, you have purchase the optional Battery Backup Write Cache Module, and configure the RAID Array Cache, using the Smart Start Bootable CDROM, run the Smart Array Configuration Utility, and configuire the Array as 75% Write, and 25% Read.

Are the disks 10k or 15k?

Author Comment

ID: 37011979
Thanks so much hanccocka,

Disks are 10k 2.5". I have installed a 512 Battery Backup Write Cache Module. Would I see any significant performance increase with a 1GB module?
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LVL 125
ID: 37011994
Some very rough quick calculations, assuming 10k SAS disks, average 121 IOPS per disk!

Current IOPS per RAID 5 Array

Total IOPS = (121 IOPS x 4 disks)/(0.67+4*.33))
                = 243 IOPS

RAID 10 proposed array of 4 disks!

Total IOPS = (121 IOPS x 4 disks)/(.67 + 2*.33))
                 = 363 IOPS

RAID 10 Array of 8 disks

Total IOPS = (121 IOPS x 8 disks)/(.67 + 2*.33))
                 = 727 IOPS

So if you used ALL eight disks at RAID 10, you would have a datastore delivery approx 727!

LVL 125
ID: 37011999
Yes, 1G will be better, but also do you have it CONFIGURED!

Just just plug it on and hope for the best!

You could allocate 100% Write!

Author Comment

ID: 37012018
Thanks again so much!

A delima I have is that there are 8 total slots. 4 are currently occupied with 146 GB disks. Adding 4 more 146 and making the whole thing RAID 10 will not yield enough storage space so I need to add 4 300GB disks. Can I make one RAID 10 array out of 146 AND 300GB drives or should I just create a new RAID 10 array of 4 300GB drives and convert the other array to RAID 10?
LVL 125
ID: 37012050
You can create a RAID 10 out of 146 and 300GB disks, but you will waste the space on the 300GB, because it will only use the space of the smallest disks in the set.

Best would be to create a 8 disk RAID 10 Array, otherwise, the alternative is to create a 4 disk RAID 10 array.

You can see the figures above! It depends how much gain, you want!

Author Comment

ID: 37012061
Thanks...good point.

If I created 2 seperate 4-disk RAID 10 arrays how much of a performance hit would I take compared to 1 8-disk RAID 10 array? If it is significant, I may just replace the 146GB disks with 8 300GB disks.
LVL 125
ID: 37012068
8 Disks is DOUBLE the IOPS, compared to 4 Disks!

Author Comment

ID: 37012083
Thanks...I see that BUT in AGREGATE, is there a significant IO advantage with running 1 8-disk RAID 10 array over 2 seperate 4-disk RAID 10 arrays? In other words, would I get 363 IOPS from EACH array to total 726 IOPS total? If so....it might make sense to keep the 146 drives and put 1/2 of the servers on that array and put 1/2 on the other array.
LVL 125

Accepted Solution

Andrew Hancock (VMware vExpert / EE MVE^2) earned 2000 total points
ID: 37012110
Yes, there is a significant advantage, more disks = more spindles = more performance to that single datastore.

otherwise, you've got two separate datastotes of 363 IOPS each,  so the Max IOPS per Virtual Machine disk will be 363!

To achieve you goal of MAXIMUM IOPS per server, would be to utilise ALL 8 disks in RAID 10.

But it depends if you really need all those IOPS, and whether suffering performance issues currently.

Author Comment

ID: 37012119
Great! It sounds like 6-8 300GB disks is the way to go. Thanks!!!

Author Closing Comment

ID: 37012122
Thanks for your help!!!

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