[rescue] T5220 update

Mark Brown sunrescue1 at marknmel.com
Sun Oct 29 16:16:22 CDT 2017

On 17-10-29 12:09 PM, Lionel Peterson wrote:
> While designed for SAS HDs, I assume SATA drives will work fine. I will test
> the system with 2x SATA 1 TB 7200 RPM drives later this week, my drive sleds
> arrived Friday (4x brand-new HD sleds for about $40 shipped). I may add two
> 240 Gig SATA SSDs as boot devices. Any reason, other than lower performance
> and reliability compared with SAS drives not to use SATA drives?
SATA rust can certainly be lower performance in the form of IOPS, since 
the SAS drives on SUNs were 10K RPM disks (generally). The SAS bus is 2 
X 3Gb/s. It's a two channel bus for performance and reliability.
Having said that, I don't think that any SAS spinning rust can actually 
saturate the SAS bus unless the data is in the cache on the disks. (and 
the caches are probably pretty small....)

Modern SATA SSD's can overcome the throughput and IOPS issue, but will 
only use half of the SAS bus.B  The best throughput you could achieve is 
3Gb/s.B  (and you might actually do this.....)

I've swapped in some Intel SSD's on our performance harness at the 
office (4 x SUN T4's).B  This works well, but if I remember, Solaris 
pukes some superfluous error messages about the the SAS bus.B  One needs 
to be careful with the multi-pathing on the root drives (since the other 
path was the other lanes of the SAS bus).B  I think I needed to disable 
it, but I'm not sure I trust those old brain cells....

Have fun!


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