Re: High CPU usage (up to server hang) under heavy I/O load

Mark Watts
2004-08-16T12:11:39Z

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> On Llu, 2004-08-16 at 10:13, Mark Watts wrote:
> > Would this also mean that if I stick a 64bit SATA raid card (a 3Ware
> > 8506-4LP in this case) into a 32bit pci slot, then I/O is always going to
> > suck badly?
> >
> > ... cos I do, and I/O sucks :)
>
> Seperate issue.
>
> 64bit DMA is 64bit addressing (ie can DMA from above 4GB). 64bit wide
> slot is double the speed for transfers. The 3ware 8xxx I thought could
> do 64bit addressing although the driver seems to indicate it cannot,
> so with over 4Gb it would hurt.

We're running Dual Opterons (Tyan S2875 boards) with 2GB ram.
These boards only have 32bit pci slots so we're already not using the full
potential of the 3Ware.
Basically write performance is a major bottleneck (hardware raid-5 with 250GB
sata drives) and writing anything over a few meg usually causes the machine
to stall while the write occurs.

- --
Mark Watts
Senior Systems Engineer
QinetiQ Trusted Information Management
Trusted Solutions and Services group
GPG Public Key ID: 455420ED

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