I'm just setting up a SuperMicro system which has twin SATA disks on an Intel IHC7 RAID-capable controller.
The system came with Fedora 5 pre-installed, which I will be removing and replacing with CentOS 4.5. But before doing so, I've been having a look at how the original vendor configured it.
When I've built systems previously, I've disabled any RAID controller and used kernel software RAID-1, set up per-partition, and this has worked well.
This system is currently set up with hardware RAID enabled, which is detected by the kernel device mapper. I can see what it has found using "dmraid" with -b, -r and -s. A single physical volume was created on the mapped RAID-1 device, and then logical volumes created on that.
My question is: which kind of configuration will generally give me better performance? To use the IHC7 RAID-1 as currently set up, or to use Linux software RAID-1 as I am used to doing? Any other reasons to choose one over the other?
Thanks in advance for any insights.
Cheers Tony
Tony Mountifield spake the following on 7/17/2007 10:32 AM:
I'm just setting up a SuperMicro system which has twin SATA disks on an Intel IHC7 RAID-capable controller.
The system came with Fedora 5 pre-installed, which I will be removing and replacing with CentOS 4.5. But before doing so, I've been having a look at how the original vendor configured it.
When I've built systems previously, I've disabled any RAID controller and used kernel software RAID-1, set up per-partition, and this has worked well.
This system is currently set up with hardware RAID enabled, which is detected by the kernel device mapper. I can see what it has found using "dmraid" with -b, -r and -s. A single physical volume was created on the mapped RAID-1 device, and then logical volumes created on that.
My question is: which kind of configuration will generally give me better performance? To use the IHC7 RAID-1 as currently set up, or to use Linux software RAID-1 as I am used to doing? Any other reasons to choose one over the other?
Thanks in advance for any insights.
Cheers Tony
I won't go into the whole "fakeraid" rant, but the software raid drivers are very mature and have been working well for years, but the dmraid code is much newer, and probably not quite as stable.
use only the linux software raid. It's perfectly stable even under high loads here.
Tony Mountifield wrote:
I'm just setting up a SuperMicro system which has twin SATA disks on an Intel IHC7 RAID-capable controller.
The system came with Fedora 5 pre-installed, which I will be removing and replacing with CentOS 4.5. But before doing so, I've been having a look at how the original vendor configured it.
When I've built systems previously, I've disabled any RAID controller and used kernel software RAID-1, set up per-partition, and this has worked well.
This system is currently set up with hardware RAID enabled, which is detected by the kernel device mapper. I can see what it has found using "dmraid" with -b, -r and -s. A single physical volume was created on the mapped RAID-1 device, and then logical volumes created on that.
My question is: which kind of configuration will generally give me better performance? To use the IHC7 RAID-1 as currently set up, or to use Linux software RAID-1 as I am used to doing? Any other reasons to choose one over the other?
Thanks in advance for any insights.
Cheers Tony
In article f7iufv$1cc$1@softins.clara.co.uk, Tony Mountifield tony@softins.clara.co.uk wrote:
My question is: which kind of configuration will generally give me better performance? To use the IHC7 RAID-1 as currently set up, or to use Linux software RAID-1 as I am used to doing? Any other reasons to choose one over the other?
Thanks for the responses, confirming what I thought: disable SATA RAID and use Linux software RAID for mirroring. So that's what I've done.
It appears that my Centos 4.4 install didn't know about dmraid devices anyway.
Cheers Tony
On 18/07/07, Tony Mountifield tony@softins.clara.co.uk wrote:
In article f7iufv$1cc$1@softins.clara.co.uk, Tony Mountifield tony@softins.clara.co.uk wrote:
My question is: which kind of configuration will generally give me better performance? To use the IHC7 RAID-1 as currently set up, or to use Linux software RAID-1 as I am used to doing? Any other reasons to choose one over the other?
Thanks for the responses, confirming what I thought: disable SATA RAID and use Linux software RAID for mirroring. So that's what I've done.
It appears that my Centos 4.4 install didn't know about dmraid devices anyway.
I personally would give fakeraid a because the hardware chipset wouldn't take as much CPU time as soft-raid. Why are you using 4.4 instead of 4.5 as you mentioned in your previous post?
Alvin Chang wrote:
I personally would give fakeraid a because the hardware chipset wouldn't take as much CPU time as soft-raid.
um, the hardware chipset is simply SATA channels. the 'raid' is done in the device drivers (and in the BIOS for startup/configuration).
I'd MUCH rather have the OS managing the raid IO queues, it will do a far better job of it.
Alvin Chang spake the following on 7/18/2007 6:34 AM:
On 18/07/07, Tony Mountifield tony@softins.clara.co.uk wrote:
In article f7iufv$1cc$1@softins.clara.co.uk, Tony Mountifield tony@softins.clara.co.uk wrote:
My question is: which kind of configuration will generally give me
better
performance? To use the IHC7 RAID-1 as currently set up, or to use
Linux
software RAID-1 as I am used to doing? Any other reasons to choose one over the other?
Thanks for the responses, confirming what I thought: disable SATA RAID and use Linux software RAID for mirroring. So that's what I've done.
It appears that my Centos 4.4 install didn't know about dmraid devices anyway.
I personally would give fakeraid a because the hardware chipset wouldn't take as much CPU time as soft-raid. Why are you using 4.4 instead of 4.5 as you mentioned in your previous post?
Fakeraid does NOT take less CPU cycles. Fakeraid chipsets do not have any processors to offload the work from the CPU. Fakeraid is just software raid hidden in the bios level. Without the software drivers, it is nothing.
In article ecf6a5280707180634h626fcf6jf89d561bdee75dab@mail.gmail.com, Alvin Chang alvin.chang@gmail.com wrote:
Why are you using 4.4 instead of 4.5 as you mentioned in your previous post?
I just haven't got around to downloading the 4.5 ISOs yet. I'm only doing a server install, so have been using my 4.4 ISO for installation and then yum update to get up to 4.5.
Cheers Tony
Alvin Chang wrote:
On 18/07/07, Tony Mountifield tony@softins.clara.co.uk wrote:
In article f7iufv$1cc$1@softins.clara.co.uk, Tony Mountifield tony@softins.clara.co.uk wrote:
My question is: which kind of configuration will generally give me
better
performance? To use the IHC7 RAID-1 as currently set up, or to use
Linux
software RAID-1 as I am used to doing? Any other reasons to choose one over the other?
Thanks for the responses, confirming what I thought: disable SATA RAID and use Linux software RAID for mirroring. So that's what I've done.
It appears that my Centos 4.4 install didn't know about dmraid devices anyway.
I personally would give fakeraid a because the hardware chipset wouldn't take as much CPU time as soft-raid. Why are you using 4.4 instead of 4.5 as you mentioned in your previous post?
There is a reason it is called FAKEraid. They provide zero cpu offloading, they do not come with a chip that does raid processing let alone a battery backed up write cache. The chipset only handles SATA or ATA channels.
Oh, if you want to try the hardware raid is faster than software raid line, then I have got news for you. Some time back, there was this i960 chip from Intel that was very popular on hardware raid solutions. It sucked. It sucked big time. Yes, it did offload a fair bit of cpu processing from the AMD/Intel cpus then but the i960 was so slow, using software raid was just a no brainer since you get twice the speed for a 10% cpu load.
Today, hardware raid come with big memory caches and that is the only reason they are faster than software raid in certain cases like raid5. Any hardware raid card that does not come with a memory cache is not likely to be much faster than a software raid solution especially when using the more complicated raid arrays like raid5/6. You will notice that products from 3ware and Areca all now come with memory caches. There is no such thing as a cheap hardware raid card.
On 19/07/07, Feizhou feizhou@graffiti.net wrote:
Oh, if you want to try the hardware raid is faster than software raid line, then I have got news for you. Some time back, there was this i960 chip from Intel that was very popular on hardware raid solutions. It sucked. It sucked big time. Yes, it did offload a fair bit of cpu processing from the AMD/Intel cpus then but the i960 was so slow, using software raid was just a no brainer since you get twice the speed for a 10% cpu load.
I had that card... LOL!
Thanks for the correction.
I start wondering how on earth Intel put those chips on...
Feizhou spake the following on 7/18/2007 11:58 PM:
Alvin Chang wrote:
On 18/07/07, Tony Mountifield tony@softins.clara.co.uk wrote:
In article f7iufv$1cc$1@softins.clara.co.uk, Tony Mountifield tony@softins.clara.co.uk wrote:
My question is: which kind of configuration will generally give me
better
performance? To use the IHC7 RAID-1 as currently set up, or to use
Linux
software RAID-1 as I am used to doing? Any other reasons to choose one over the other?
Thanks for the responses, confirming what I thought: disable SATA RAID and use Linux software RAID for mirroring. So that's what I've done.
It appears that my Centos 4.4 install didn't know about dmraid devices anyway.
I personally would give fakeraid a because the hardware chipset wouldn't take as much CPU time as soft-raid. Why are you using 4.4 instead of 4.5 as you mentioned in your previous post?
There is a reason it is called FAKEraid. They provide zero cpu offloading, they do not come with a chip that does raid processing let alone a battery backed up write cache. The chipset only handles SATA or ATA channels.
Oh, if you want to try the hardware raid is faster than software raid line, then I have got news for you. Some time back, there was this i960 chip from Intel that was very popular on hardware raid solutions. It sucked. It sucked big time. Yes, it did offload a fair bit of cpu processing from the AMD/Intel cpus then but the i960 was so slow, using software raid was just a no brainer since you get twice the speed for a 10% cpu load.
Today, hardware raid come with big memory caches and that is the only reason they are faster than software raid in certain cases like raid5. Any hardware raid card that does not come with a memory cache is not likely to be much faster than a software raid solution especially when using the more complicated raid arrays like raid5/6. You will notice that products from 3ware and Areca all now come with memory caches. There is no such thing as a cheap hardware raid card.
The i960 doesn't count, since it hasn't been used for a while. I think it was designed as a printer rendering engine processor, and was never designed for the load that raid imposed.
Oh, if you want to try the hardware raid is faster than software raid line, then I have got news for you. Some time back, there was this i960 chip from Intel that was very popular on hardware raid solutions. It sucked. It sucked big time. Yes, it did offload a fair bit of cpu processing from the AMD/Intel cpus then but the i960 was so slow, using software raid was just a no brainer since you get twice the speed for a 10% cpu load.
Today, hardware raid come with big memory caches and that is the only reason they are faster than software raid in certain cases like raid5. Any hardware raid card that does not come with a memory cache is not likely to be much faster than a software raid solution especially when using the more complicated raid arrays like raid5/6. You will notice that products from 3ware and Areca all now come with memory caches. There is no such thing as a cheap hardware raid card.
The i960 doesn't count, since it hasn't been used for a while. I think it was designed as a printer rendering engine processor, and was never designed for the load that raid imposed.
I did say that the i960 WAS very popular some time back.
But yes, I suppose I was not very explicit on the fact that although hardware raid cards today come with much more powerful processors, they still need memory cache to get performance benefits over software raid.
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