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how install a H700 controller in a PE2950III

Posted on 2012-09-22
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I have a Power Edge 2950III with a PERC 6/i (with 6 SATA HDD's) and I want to replace it with a Dell PERC H700.

I'm looking for details and considerations in terms of hardware (extra components, etc) that I need to be aware of, to do the installation with my current configuration (my plan is to install the new controller then after few months start a progressive HDD replacement).
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Question by:moralesrd
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by:David
ID: 38424661
Get an external enclosure and use both controllers and sets of disks at the same time.  Then you can boot the system to a USB flash drive running linux.  Then use one of the free partition managers to clone and resize the PERC 6/i based LUN(s) to the H700.
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by:moralesrd
ID: 38424806
I don't understand what are you saying; I just want to "replace" the PERC 6/i with a H700 (the content of the raid partition at this point is irrelevant, because I can repartition everything from the beggining) and boot normally from Windows.
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by:David
ID: 38424829
If you don't need the data then just crack open the case to see if there is a free slot and the cabling from the card to the backplane is compatible and then just do it.

If the cabling is not compatible, then you are going to need to purchase an external enclosure with an embedded expander and appropriate cabling.  This is a SAS-2 controller so you should get a SAS-2 (6gbit backplane).

Dell will be happy to tell you what products they have that will do the job for free if you use their 800 number. You can go to the support.dell.com site and log in and use their software to tell you the configuration you bought.   That is easiest path.

But understand that the H700 is SAS-2, your backplane is SAS-1, so even if there was a compatible cable then you would still be stuck at 3Gbit/sec instead of the 6Gbit/sec capability of the H700.  Personally, since you only have 6HDDs, I don't see this being a cost-effective upgrade unless you are planning to go to RAID6.

If you want a speed bump, buy a pair of small SATA SSDs, use host-based RAID1, and then move all your index files, scratch table space, swap, and anything else that is I/O intensive to those two drives.  Since they are SSD you don't have to worry about a solid mount to prevent vibration, and you just need 2 plain vanilla SATA ports.

For the same price as that controller, you can get a pair of nice SSDs and get 50,000 random I/Os per second compared to a few hundred on a H700 with a RAID6 LUN.
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by:moralesrd
ID: 38424887
mmmmm... in fact I do have only SATA2 (500GB) drives in RAID-0 and my plan is to buy 6 SSD and configure it in RAID-0 as well; of course, I'm looking for the H700 to increase the read/write performance (currently in 600 MB/sec).

This server is used only to processing big images, in fact the block size (in the raid configuration) was set to 512KB to get the better performance.

So, are you saying that using a H700 will not improve the read/write performance, with the current HDD and/or a new set of SSD?
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by:PowerEdgeTech
ID: 38424903
First, know that the H700 is not officially supported in the 9G servers, so it may or may not work, but I have seen several people having done it "successfully".  A few of things you should know:

1.  You will need to compare the H700 controller to the PERC 6 - physically ... it would need to go in the dedicated/integrated slot designed for the PERC, so you'd need to make sure that it will actually fit in the area designed for that card.

2.  The H700 (SFF-8087) takes a different SAS cable than the PERC 6 (SFF-8484), so you would need to obtain the proper cabling.

3.  PERC 6 Virtual Disks are compatible with the H700, so technically, you could migrate the disks directly, however, you would make sure the PERC 6 firmware is up to date.
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by:David
ID: 38424920
If you want best possible performance, you need to get a LSI SAS JBOD HBA.  The firmware in that controller will be a bottleneck.  The backplane is also going to be a bottleneck.  

Best and cheapest way to do this is buy 2 x 4-port PCIe-based SATA-3 controllers.  With the right SSDs you should easily be able to sustain 1500 MB/sec if you had PCIe 2.0 based controllers and your motherboard could handle it.
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by:moralesrd
ID: 38424928
Perfect... just two more questions here about performance?

if I'm currently getting a 600MB/sec read/write transfer rate with the current Perc 6/i (and SATA-II HDD); how much additional performance would I get using the new controller in the same server?

The second question is: how much performance would I get using SSD with this hardware configuration, based in the technology limitations of the server?
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by:David
ID: 38424950
You will have to study the motherboard diagram and look at the bus interface chips.  I have no idea what the limit will be w/o doing that.

RAID0,1, 10 will always be done much more quickly and efficiently with host-based/software RAID than with any RAID controller on multi-core CPUs. 10 years ago it was a different story.  

The H700 controller firmware virtualizes and remaps all I/O and adds a great deal of latency. You wouldn't notice it on mechanical drives, but it will be quite noticeable on SSDs.  You want to take out all bottlenecks, which includes the SAS1 expander, the megaraid firmware (inside the H700) and all the additional latency to get things in and out of that controller.

With software RAID, the RAID0 mapping is all done in the kernel and the overhead is effectively unmeasurable.  You do the RAID calculation in nanoseconds in the kernel, but if you move it to H700 they end up taking microseconds.  Big difference.
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by:moralesrd
ID: 38425087
Ok... let me see if I understand correctly.... you said before: "But understand that the H700 is SAS-2, your backplane is SAS-1, so even if there was a compatible cable then you would still be stuck at 3Gbit/sec instead of the 6Gbit/sec capability of the H700"; that means that I won't get a bigger bandwidth but, then you said "You do the RAID calculation in nanoseconds in the kernel, but if you move it to H700 they end up taking microseconds.  Big difference."

How I could interpret both statements?
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by:David
ID: 38425219
Electrically you can hook any of this together, providing you get the cabling correct ... but it will sync up at lowest common denominator ... SAS-1, which is 3Gbit/secs max.

But if you get a SATA-3 controller, and direct attach via 4 x SATA-3 ports, then each disk gets the full SATA-3 speed of 6Gbits/sec.  

Choose wisely on the SATA-3 controller. Make sure each drive gets the full 6bits/sec, and there is no internal mux that shares all the bandwidth into something less than the sum.  Real-world you should be able to get at least 1.5GB/sec with for high-end SATA-3 SSDs, and at least 100,000 random IOPs depending on the RAID settings.
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by:PowerEdgeTech
ID: 38425254
How would you connect the drives to the controller and power, if not through the backplane?    It can't be removed, and if it is the limiting factor, then where is the benefit?
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by:David
ID: 38425296
These are SATA SSDs.  No issues with heat or vibration, they are small, and are even hot swap because all SATA disks are.  You don't need an expensive enclosure.   Get SATA-3 card that doesn't use an expander that has individual SATA-3 cables.

You only need to hot swap when you have a failure.  Is it worth $2000 for a SAS-2/SATA-3 backplane to save 5 minutes when/if a SSD fails?  Ask your comptroller if that is a wise investment.  

Rubber band a few together and mount them internally. Heck. You can duct tape them to the case for all that it matters.  It just isn't necessary to put SSDs in hot swap drive bays behind expensive backplanes.  They don't need it.
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Author Comment

by:moralesrd
ID: 38425443
Well, now I'm confused again... my initial idea of installing a H700 controller is to get better performance reading/writing files (big ones); so, after all seems like IF I install SSD disks in the current Perc 6/i, I should get about the max performance from the Perc 6/i, because, in theory the max transfer rate would be about 1482MB/s (3Gb/s), I'm a right?

I'm using 6 SATA-II HDD in Raid-0 and just getting 600MB/s transfer rate, so, that means that I'm way below the max capacity for the Perc 6/i controller, right?

If I install the H700 controller with the current SATA-II HDD's I would get a better transfer performance or is just that I reached the max of the HDD transfer capacity?
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by:andyalder
ID: 38425536
Perhaps you would be better off using NAND flash on a PCIe card rather than SSDs; no relatively slow SATA bus to worry about, no cables even. Not cheap of course so you won't be able to store the files on it permanently but you could move them to it for processing and then copy them elsewhere afterwards.
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by:David
ID: 38425551
Lets regress a bit and set some parameters.  How many GB usable do you need, and how much throughput/IOPs do you need, and what is your budget?   A flash-based PCIe card is a good fit, just like a half-dozen SSDs are and even a H700+SAS-2 SSDs are, it comes down to what meets your constraints.

You really need to ask what meets your constraints instead of going down the path of how to use the H700.  This configuration is not necessarily best.
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Author Comment

by:moralesrd
ID: 38425570
Well... in terms of space needed couple TB's (2 or 3) are good enough (I already have another device with 6TB's for storage not that fast of course for old data).

how much speed do I need? more is better...

what is my budget? cheapest option is better or at least an scalable option...
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by:andyalder
ID: 38425907
How much space do you need during the image processing part? Is it viable to transfer the images to a super fast area of flash, process them and then transfer them back to relatively slow storage?
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by:moralesrd
ID: 38426304
well, just for the temp folder I need about 500GB and even more depending of the project... the problem here is that moving images to a slow repository will be add another bottleneck copying images from one server to another.

That's why I have 6 HDD's connected in RAID-0 in one huge partition, that even when is not the most efficient, is the fastest combination that I found.... and is the reason of the things that I'm trying to do..
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by:moralesrd
ID: 38427097
Here... I'm looking in the 512GB Crucial m4 2.5-inch SATA 6Gb/s as possible SSD option, this particular disk have 500MB/s data transfer speed and I wonder IF I install 3 disks in RAID-0 I could get the maximum performance from the current PERC6/i controller????

The other option seems to forget the SSD disks and maybe move forward with 6 HDD WD Velociraptor WD1000DHTZ 1TB 3.5" that have 200MB/s data transfer speed, and get the about 1GB/s combined in RAID-0... and forget about everything else.... what do you think?
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by:David
ID: 38427204
The best you can expect to get with that config and the PERC6 would be transfer rate of around 850MB/sec.  (The PERC uses a LSI 1068e controller, which is 3Gbits/sec max per port and 8 lanes, so with 8 drives the most you could get in perfect world is 2.4Gbits/sec)

Conversely with native windows software-based RAID0 and a pair of PCIe SATA-3 cards, you could be able to sustain around 1600MB/sec in pure sequential I/O .. provided your bus can handle it and each port had full 6Gbit/sec capability.

But look at the schematics.  You need 2 lanes to get 500MB/sec, so you need a card that uses 4 lanes to get the best-case 1000MB/sec, and then a slot in the motherboard that can do it.  Look at the motherboard specs and see how many lanes your PCIe slots support and whether they are PCIe 1.0 or 2.0 or something else.
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Author Comment

by:moralesrd
ID: 38427488
The PE2950III does not come with PCIe 2.0, that doesn't means that the SATA-III adapters will be runing at 3Gb/s?
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by:David
ID: 38427510
The max data rate that PCI 1.x is capable of delivering is 250MB/sec per lane. (You have to allow 20% overhead in PCIe 1x)  So if you have a X4 slot, then most you can get is 1000MB/sec, no matter how many SSDs you have.  


I looked at the mobo, it has the intel 5000x chip.  So each PCIe X8 port is good for up to 3.2 GBYTES/sec.   So bottleneck won't be the bus.  It will be the controller card(s)
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Author Comment

by:moralesrd
ID: 38429232
well, the server only has 1 PCIe X8 (the second one is 4X), and I'm not finding any raid adapter 8x and the 4X that I found are in the range of $200.... so, the question here would be again.... how much speed transfer would I get with a H700 (that I can find used in about $300)????
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by:David
ID: 38429302
The max you can ever get is 250MB/sec per port real-world.  3xSSDS = 750MB/sec.  4 SSDs = 1000MB/sec.
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by:David
ID: 38429310
P.S.  You DO NOT need a RAID controller.  RAID0 has no measurable overhead unless you have a rather expensive analyzer.

Let the O/S do the RAID.  Look for NON-RAID controllers.
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Author Comment

by:moralesrd
ID: 38430821
So, I just need to find a PCIe 1.0 4x SATA-3 adapter to get a better performance, right?
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Accepted Solution

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David earned 2000 total points
ID: 38430841
Almost.  You need to make 100% sure that ALL ports get the full SATA-3.  Some vendors will gladly pull a fast one and say it is SATA-3 compatible, but fine print is that each port is limited to 3Gbits/sec.

Call the tech support for whatever product you select, ask for pre-sales, and tell them flat-out you are hooking up some high speed SSDs to each port and want to make sure you get the full speed on each port as well as the full total of approx 500GBytes/sec x 4 ports.

Then use the native host-based software RAID.    Avoid any unit that has built-in RAID firmware.  They will slow you down. You can't get any inexpensive RAID chips that won't be a bottleneck.
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Author Comment

by:moralesrd
ID: 38435000
I think that an LSI or HighPoint card may work, so I will try to find the cheapest ssd that I can find then think about the card, because the first cost $200 and the second one $100 and I need to understand the differences between the two (that are both PCIe 1.0 4x compatible and also 4 ports)
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