C-Otto

Software RAID performance

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Hello!

I'd like to buy a system with 4 drives in RAID5 configuration soon to have something fast and reliable to boot from over the network. The main question is, of course, the RAID controller. I can start with a board with good onboard SATA ports (so not over PCI) and use Linux software RAID, but I can also use a Areca controller for 350 Euro.

Is there any useful benchmark that compares good RAID cards with the current Linux kernel?

Thanks a lot,

Carsten Otto

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Hello!

I'd like to buy a system with 4 drives in RAID5 configuration soon to have something fast and reliable to boot from over the network. The main question is, of course, the RAID controller. I can start with a board with good onboard SATA ports (so not over PCI) and use Linux software RAID, but I can also use a Areca controller for 350 Euro.

Is there any useful benchmark that compares good RAID cards with the current Linux kernel?

Thanks a lot,

Carsten Otto

I think actual [REAL] RAID card support is more important under Linux and needs to considered before performance.

http://linuxmafia.com/faq/Hardware/sata.html

Most of the RAID cards are SW raid [FAKE].

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I don't talk about importance, but performance. Moreover I know what cheap RAID cards are, the 350 Euro card is not that cheap.

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linyucks software raid is good enough, lots of people use it in production systems. I have several production

oracle systems that use software mirroring so I can go across controllers. If linux isnt your bag, give solaris10 x86 a try.

(so not over PCI)
any controller over pci will be fine, its still faster than gig ethernet...

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linyucks software raid is good enough, lots of people use it in production systems. I have several production

oracle systems that use software mirroring so I can go across controllers. If linux isnt your bag, give solaris10 x86 a try.

I will try Linux software RAID.

any controller over pci will be fine, its still faster than gig ethernet...

The problem is that four disks and one GigE card saturate the PCI bus. That is why I'd like to buy a board with decent GigE chip (via PCI Express), which is not the problem. Moreover I'd like to see my SATA ports connected via PCI Express. Here I can't even find the correct information in the mainboards' manuals. Cheap (non-raid) Add-On cards are not (yet) supported by Linux, so this is no option.

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The problem is that four disks and one GigE card saturate the PCI bus. That is why I'd like to buy a board with decent GigE chip (via PCI Express), which is not the problem. Moreover I'd like to see my SATA ports connected via PCI Express. Here I can't even find the correct information in the mainboards' manuals. Cheap (non-raid) Add-On cards are not (yet) supported by Linux, so this is no option.

theres always pci-X (1GB/s) I can get 540MB/s r/w off of 12 15000rpm drives striped :)

besides gigE is going to max out about 70MB/s regardless of what your disks are... thats about half of the bandwidth of a 32bit/33Mhz pci slot. and you only do long sustained sequential reads in benchmark programs anyways.

Anyhow I dont mean to seem negative, but for a small pc based file server, with 4 ata drives and 1000Mb ethernet, regardless of how much money you spend: gigE and the seeks/sec of 4 7200 drives are going to constrain you more than the bus. I would argue that some cheap+big rebated pata drives ($100 300GB Seagates) and a couple of $10 sil0680 cards. Will perform the same as a $350 raid card most of the time.

New Raptors and a raid card with lots of cache is a different story, but thats $1000 more for half the space...

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theres always pci-X (1GB/s) I can get 540MB/s r/w off of 12 15000rpm drives striped :)

besides gigE is going to max out about 70MB/s regardless of what your disks are... thats about half of the bandwidth of a 32bit/33Mhz pci slot. and you only do long sustained sequential reads in benchmark programs anyways.

Anyhow I dont mean to seem negative, but for a small pc based file server, with 4 ata drives and 1000Mb ethernet, regardless of how much money you spend: gigE and the seeks/sec of 4 7200 drives are going to constrain you more than the bus. I would argue that some cheap+big rebated pata drives ($100 300GB Seagates) and a couple of $10 sil0680 cards. Will perform the same as a $350 raid card most of the time.

New Raptors and a raid card with lots of cache is a different story, but thats $1000 more for half the space...

I currently have GigE over PCI and Software RAID 0 with two 7200rpm drives in my workstation. I frequently have problems with a saturated PCI bus. My upload speeds (or overall performance) makes a noticable jump when I turn off my music (which goes over the PCI bus). So please understand that I'd like to have something better for my (costy) server. PCI-X is no option, because I can't find a suitable board. Additionally I need some SATA controller for that, too (hardware RAID would be expensive). I think I will go with a board that does GigE Intel PCIe and has four SATA ports connected directly to the soutbridge (or so) without PCI. That should do the trick and is not expensive at all.

PS: I do more than 70 MB/sec with my standard PCI GigE, at least when the data goes from/to the RAM.

PPS: The system does not only provide data to me, but to the whole network (several hundred users).

Bye,

C-Otto

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