nVidia FakeRAID
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So, using SCSI or ATA commands, whatever is handy... how are you piercing the veil of hardware array encapsulation? Either it is a SmartArray P400 or a EMC VNX or an HUS whatever... how are you getting to the underlying devices past the array encapsulation?
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@scottalanmiller said:
There is chipset RAID that does not use the CPU and is hardware RAID. It encapsulates. This is fact. The nVidia stuff that I have seen first hand uses the CPU (no hardware RAID) and does not abstract anything (no encapsulation.)
Unless it has a dedicated CPU, where do you think those cycles are coming from?
nVidia doesn't make dedicated RAID chips.
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Further derailment (ignore at will)
At what point do you get a reasonable controller for home / soho use? (initially 4 drives, expanding to 8 soon)
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&IsNodeId=1&N=100007607 50001833 50001329
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@PSX_Defector said:
Unless it has a dedicated CPU, where do you think those cycles are coming from?
nVidia doesn't make dedicated RAID chips.
No Harware RAID maker does. They buy them from other vendors. Super high end devices like NetApp use custom ASICs so you could argue that they are chip makers. But normal hardware RAID uses ARM, Power or possibly Sparc chips. Nvidia, to do hardware RAID like AMD, would put the RAID processing into the RAID chipset.
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@scottalanmiller said:
So, using SCSI or ATA commands, whatever is handy... how are you piercing the veil of hardware array encapsulation? Either it is a SmartArray P400 or a EMC VNX or an HUS whatever... how are you getting to the underlying devices past the array encapsulation?
You query it through whatever protocol you are using.
http://www.tinkertry.com/msminstallonwindows/
In dedicated hardware RAID, you talk to the card, the card tells you what you need to know. In chipset based RAID, it talks to the southbridge (Intel) or HT chip (AMD). Software RAID presents to the OS individual drives, it's ganged up logically to the OS specs.
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@MattSpeller said:
Further derailment (ignore at will)
At what point do you get a reasonable controller for home / soho use? (initially 4 drives, expanding to 8 soon)
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&IsNodeId=1&N=100007607 50001833 50001329
Easy answer... when it makes sense
It's not cut and dry. Software RAID is completely viable except for on VMware where it is impossible, for a home lab. Even on Windows. In production Windows / HyperV software RAID is not really very viable, but other than that, OS and FS level software RAID is often the more enterprise choice. It really comes down to what the purpose of the lab is (if it is to learn hardware RAID, you need hardware.) But if the RAID is only to combine drives into an array, you don't need hardware for that.Size of the array is not a factor unless you have controller limitations (AMD hardware limits to just two drives, for example.)
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@PSX_Defector said:
In dedicated hardware RAID, you talk to the card, the card tells you what you need to know.
It tells you what it wants to tell you. The array is 100% encapsulated and the array tells you want it wants you to believe. It exposes at will and never by accident. You can't read or write to individual drives, only the array.
With FakeRAID not only can you, but often you will by accident. If the driver crashes, for example, you would suddenly have access to two (or more) raw drives with the system having no idea that there was supposed to be RAID there. With hardware RAID, that can't happen.
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@scottalanmiller said:
@PSX_Defector said:
Unless it has a dedicated CPU, where do you think those cycles are coming from?
nVidia doesn't make dedicated RAID chips.
No Harware RAID maker does. They buy them from other vendors. Super high end devices like NetApp use custom ASICs so you could argue that they are chip makers. But normal hardware RAID uses ARM, Power or possibly Sparc chips. Nvidia, to do hardware RAID like AMD, would put the RAID processing into the RAID chipset.
Now you are confusing everything.
By your definition, southbridge/HT based RAID setup is ALWAYS "fakeRAID". A dedicated processor, be it from LSI, Intel, or any number of vendors, is ALWAYS hardware RAID. Anything configured at the OS level is ALWAYS software RAID.
Again, this is the same stupid arguments that have been going on since 2002. Calling it "fakeRAID" is just stirring up the pot.
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Any hardware RAID card can accept arbitrary commands and relay them to the drives if it wants to, that would be an optional component. But it is always at the hardware's discretion. FakeRAID can't stop you, it doesn't have the power. No matter what the implementation, FakeRAID can be disabled in software and the devices messed with without the RAID system being able to stop you or, even more importantly, without it knowing.
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@scottalanmiller said:
With FakeRAID not only can you, but often you will by accident. If the driver crashes, for example, you would suddenly have access to two (or more) raw drives with the system having no idea that there was supposed to be RAID there. With hardware RAID, that can't happen.
Love to see how that can happen, considering Intel/AMD/nVidia presents a single drive. So when you pop that drive off the machine, you are saying that you can access the raw file system of either drive?
Bullshit.
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@PSX_Defector said:
Love to see how that can happen, considering Intel/AMD/nVidia presents a single drive. So when you pop that drive off the machine, you are saying that you can access the raw file system of either drive?
Pop that drive off? What are you picturing?
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@PSX_Defector said:
Love to see how that can happen, considering Intel/AMD/nVidia presents a single drive. So when you pop that drive off the machine, you are saying that you can access the raw file system of either drive?
Yup, that's what FakeRAID does. We've seen it happen a lot. It's very common. How have you not run into it over and over again? People have it happen on SW regularly. That's how we know that they have FakeRAID, they accidentally see the corrupted partial filesystems (because often it is one drive out of a RAID 5 set - people using FakeRAID tend to overlap heavily with people using RAID 5.)
Doesn't happen with AMD. Like I said, they make hardware RAID.
Not when you pop that drive off, when you don't have the driver. Not sure what terms you are using there. But when you install another OS without the driver needed, for example, or the driver is removed or disabled.
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That's what you are missing. AMD, LSI, Adaptec... they present a single drive (the array) to the system. That's hardware RAID.
Intel and nVidia present the individual drives because they are nothing but SATA or SAS controllers, no hardware RAID. They let the system make the RAID at another level in software. Intel makes both kinds, so they are tough to track down.
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Because AMD is real hardware RAID that is fully encapsulated, I've seen datacenters sell HP (Asus) desktops to customers as servers with hardware RAID because customers are not used to true hardware RAID on a desktop device and assume that it must be a real server because of it.
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@scottalanmiller More derailing: Apologies for not asking my question correctly - at what price point do you get something worth having? I have an old Dell tower that will be my VMware home server, it's receiving 4x 2TB (another 4 later when they're cheaper or I run out of space). It came with an LSI card but it was dead (reason the box was retired.) I'll need to purchase one to replace it and get this server up and running.
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@MattSpeller said:
@scottalanmiller More derailing: Apologies for not asking my question correctly - at what price point do you get something worth having? I have an old Dell tower that will be my VMware home server, it's receiving 4x 2TB (another 4 later when they're cheaper or I run out of space). It came with an LSI card but it was dead (reason the box was retired.) I'll need to purchase one to replace it and get this server up and running.
New, generally somewhere around $700.
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@scottalanmiller said:
New, generally somewhere around $700.
Ohhhhh brutal. The $200 ones just don't cut the mustard? This is for my own personal crap afterall.
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@MattSpeller said:
Ohhhhh brutal. The $200 ones just don't cut the mustard? This is for my own personal crap afterall.
Not really. Normally they have very underpowered CPUs and no RAM. Stick with software RAID if you are going that route. Normally the cheap ones aren't on the VMware HCL either which makes them extremely limited in their utility.
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Another factor that people forget with FakeRAID until it is too late... if your OS crashes your RAID is useless. With hardware RAID you can rebuild your RAID after a drive loss even when the system is offline. The datacenter people don't need to know if the OS is healthy, if it is on, etc. They can swap drives and let the RAID controller repair the array.
With FakeRAID there is no RAID until the OS works and is healthy. So even if you replace a drive, the array might be unable to repair itself.
Dealing with someone facing this problem right now. System crashed with the RAID array lost a drive and won't boot. Not the OS is having issues and there is no RAID at all.
