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Disk Management on PowerEdge R910
On a PowerEdge R910 configured with the 16 internal disk backplane, is it possible to manage / configure select groups of disks with individual H700 controllers? Would there be a performance benefit to running the OS (Windows) via integrated RAID and use a separate H700 for two other Raid1 containers, and another H700 for a Raid 5 container?
pcmeiners
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February 21st, 2012 13:00
Depends....
If the load is light two controller will produce higher throughput. If the load is medium -high then two controller would increase the CPU/IRQ load thus lowering the overall server performance, NIC interface throughput would also decrease. Then you need to consider, with two controllers, if functions such as temp files, db temp files, pagefile are placing traffic between the controllers, this would take up bus bandwith , not normally placed on the bus by a single controller.
Then consider bus saturation. If you have SAS 6.0 drives your not going to saturate the H700, if it were an old/low end controller (SAS 3.0) you would saturate the controller, then a second controller would be called for.
For maximum proformance, you would want to use an SSD raid1, (for safety, with a hotspare or at least a cold spare on hand ) for at least the tempDBs, transaction logs, tempfiles, pagefile, logs, and for good measure the OS. Under ANY circumstances the OS should be separated from the data, at minimum a separate partition, at best on a separate spindle set from the data . To complicate your question, a couple SSDs added to the controller could saturate it, but I doubt the SSDs with the setup as above would
Saturation....
www.dell.com/.../perc-technical-guidebook.pdf
In small disk drive configurations (one to eight drives) the aggregate media rate of the disks (the speed at which the disk heads can read and write data) become the bottleneck for storage throughput. As business storage needs grow, IT centers can add more disk drives to their storage infrastructure, and the latest generation of SAS allows server performance to scale past the 3Gb/s SAS performance limitations: from 2.4 GB/s to 4.8 GB/s unidirectional.
Table 3. SAS Performance Details
SAS Generation PCI-Express Interface Approximate number of SAS HDDs required saturate bandwidth (RAID 0)
1.0 (3Gb) 1.0 8 to10
2.0 (6Gb) 2.0 16 to 20
Saturation.....
serverfault.com/.../how-many-disks-can-saturate-a-6gsas-controller-lsi-9260-8i
Benchmarks, some Dutch, benchmark in English, many of the benchmarks are for SSD and SATA, if you dig there are SAS benchmarks.....
tweakers.net/.../13
DELL-Chris H
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February 21st, 2012 07:00
Beach3141,
You won't need multiple H700's. A single H700 supports up to 16 drives in up to 8 different Virtual Disks.
To answer your question,
"Would there be a performance benefit to running the OS (Windows) via integrated RAID and use a separate H700 for two other Raid1 containers?"
There isn't as much a performance increase having a separate array for the OS than from the data, but it does separate the data from any OS issues that may arise. If separated you can simply re install the OS without effecting the data.
For the best balance of redundancy to speed you could do a 2 drive raid 1 for the OS and then a multiple drive raid 5 for the data.
Let me know how it goes.
Alan Kessner
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February 21st, 2012 08:00
This is just a theoretical question about absolute maximization of disk responses. I want to separate the OS from the raid container AND controller running SQL transaction logs, from TempDb and from backup databses... everything would be "isolated" and running on it's own controller. Would there be a noticeable performance difference with separate controllers than from running transaction logs, tempDb and backup DB all on the same controller? Production databases would run on external PowerVault MD1200. Or, does the throughput capability of the H700 vastly exceed the capability of attached 15K SAS2 disks to perform simultaneous read and write operations? This is for a 4TB Business Intelligence system.
Alan Kessner
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February 22nd, 2012 04:00
That you for the comprehensive reply. This is good information to ponder, and at least gives me enough guidance to compose a proposal bid for this project.
pcmeiners
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February 22nd, 2012 05:00
Just a note on SSDs..
I have a couple on my machine, superfast, and oddly they do not corrupt the OS like normal hard disks, even with illegal shutdown\BSODs (had plenty of BSODs due to a bad driver). They do wear out (fairly long time) , so raid is necessary, and you need to be careful as to compatibility , I would run them for a while before placing them into production, as you should with any server, no matter what hardware is involved. For a burn-in test I use prime95 and OCCT. Prime95 is good, OCCT borders on brutallity/terrorism, but if a machine is unstable OCCT will force it's colors (keep an eye on temperaturers with OCCT).
Alan Kessner
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February 22nd, 2012 06:00
Our developer / DBA is not exactly an advocate of SSD drives, so this config would be based entirely upon 300Gb SAS disks spinning at 15K. Thanks...