[Gllug] Hardware comparisons

[Richard Jones]

On Fri, Mar 23, 2007 at 06:24:37PM +0000, Alain Williams wrote:
> I'm putting together a box for a customer, cost is not the primary
> concern (I'm replacing a 40K AIX box with a dual core AMD based box),
> stability/reliability are highly desirable ... might as well get it
> fast as well.
> 
> There are a few choices, comments please:
> 
> * They wanted SCSI, I had specified SATA ... is SCSI still worth
>   the premium ? We will need a SCSI card for the DAT drive anyway.

Take a look at:

http://labs.google.com/papers/disk_failures.pdf

I would go for drives where the manufacturer is willing to give you a
long guarantee (5 years) on drives which they rate for 24/7 server
operation.  WD RE2 perhaps - but check their "limited warranty".

> * Mirroring. Is this best done by the kernel or through a RAID controller ?
>   I believe that if the kernel sees 2 drives it will do reads in parallel
>   (I believe that computers read more often than they write); it is
>   suggested that using a RAID controller will reduce bus bandwidth (write to
>   controller once which writes to the disks twice) & so make the machine faster.

Many years ago now I did tests on this and found that software RAID
was 5 times faster than hardware RAID (2000-era Pentium IIs vs. ICP
Vortex cards and a really awful Dell RAID card).  At the same time
everyone was claiming otherwise.  If you can, get the cards on spec
and test them against the expected workload.

> * Memory. Both DDR2 dual channel:
>   One supplier can provide: PC2-4200 (533MHz)
>   The other: PC2-6400 - 800MHz
>   Will the faster memory make a real difference ?

Are either/both of these ECC?

Rich.

-- 
Richard Jones
Red Hat
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