Re: quick (software versus hardware raid) question (cpu)

[Dan C Marinescu <dan_c_marinescu@yahoo.com>]

it seams to me tha SCSI_SATA_SIL works with Sil 3114!

// happy now :-)

   daniel

--- Dan C Marinescu <dan_c_marinescu@yahoo.com> wrote:

> hi there,
> 
> i have a mission critical system with an unsuported
> raid controller (4 sata channels, sil 3114). so, i
> set
> up a software raid... now, the problem is at pick
> hours, when nics hardware interrupts compete with
> the
> software raid kernel thingie... i know you avoid
> spawning threads but regarless the scheduller's
> preeptivenes, the two kernel tasks are
> scheduller-wise
> competing and this is killing my server (slowing it
> down, cpu is at 100% user and 40-60% kernel).
> another
> issue is that not being able to "see" the "bios"
> partition (controller is totally unsuported) i
> cannot
> boot (unless i go like raid 1 on /boot). so what
> about
> performance? what about scalability? if case of 1
> array (hardware raid) versus n distinct sata
> connectors, you big o notation goes like O(n)
> instead
> of O(1), no matter how smart the scheduller _is_
> implemented, for the simple reason that hardware
> interrupts are hardware interrupts... preemptive or
> not, you have to serve them sooner or later and it's
> one thing to sever 1 instead of n... another issue
> is
> reliability. if you use software raid, and the
> kernel
> goes down (for unrelated reasons) your parity
> calculations and the raid cache go down as well,
> huh?
> and the other way around... the raid goes down,
> taking
> the sata driver with him... that takes the whole
> system down, huh? well, maybe i am too pesimistic
> but
> still, the scalability concern remains! nics are
> huge
> scheduller enamies... they have to do so much with
> cpu, and transfers to system memory, in order to
> actually server thier purpose (protocols) it seams
> to
> me that there isn't much left for user-land and
> software raid... (especially when many nics and many
> satas are involved...)
> 
> in short, could you recommend me a peformant (sata
> connectors) raid controller, which is fully
> supported?
> please don't go like "make gconfig" cause i've been
> there... thanks!
> 
> regards,
>   daniel
> 
> 
> 		
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