SAS6 vs PERC6?

[Tino Schwarze]

On Wed, Apr 15, 2009 at 11:04:13AM -0700, David Sparks wrote:

> >> Has anyone tested the performance of the SAS6/iR onboard controller vs the
> >> PERC6 addon controller?
> >>
> >> The SAS6 is a very basic controller with almost no features and does not have
> >> a cache (but has dangerous drive cache support).
> > 
> > I'm not sure about the SAS6, but the SAS5 sucks in terms of performance.
> > I mean, it doesn't just suck, it really SUCKS! It's no real RAID
> > controller (no memory, so no cache). I'm considering to switch to
> > software RAID1 on a PE860 since there's no PERC available for that
> > machine.
> 
> Is the SAS5 a Fusion MPT based card? (SAS6 is)

Yes. lspci says:
02:08.0 SCSI storage controller: LSI Logic / Symbios Logic SAS1068 PCI-X Fusion-MPT SAS (rev 01)

The main problem is: No cache, no battery, therefore no write back cache
etc. For each write, it probably just duplicates the command and sends
it to both disks. It's got almost no logic, therefore the bad
performance. I'll see how it does in JBOD mode with software RAID1.

Tino.

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