[ale] Performance issue

DJ-Pfulio DJPfulio at jdpfu.com
Sun Aug 21 10:02:35 EDT 2016


On 08/20/2016 10:00 PM, Jim Kinney wrote:
> 6Gbps SAS. 12 in one array and 38 in another. It should saturate the bus.

6Gbps is the interface speed. No spinning disks can push that much data
to my knowledge - even SAS - without SSD caching/hybrids. Even then,
2Gbps would be my highest guess at the real-world performance (probably
much lower in reality).

http://www.tomsitpro.com/articles/best-enterprise-hard-drives,2-981.html

You work in a highly specialized area, but most places would avoid
striping more than 8 devices for maintainability considerations. Larger
stripes don't provide much more throughput and greatly increase issues
when something bad happens.  In most companies I've worked, 4 disk
stripes were used as the default since it provides 80% of the
theoretical performance gains that any striping can offer.  That was the
theory at the time.

Plus many non-cheap arrays will have RAM for caching which can limit
actual disks being touched. Since you didn't mention EMC/Netapp/HDS, I
assumed those weren't being used.

Of course, enterprise SSDs changed all this, but would be cost
prohibitive at the sizes you've described (for most projects).  I do
know a few companies which run all their internal VMs on RAID10 SSDs and
would never go back. They aren't doing "big data."



More information about the Ale mailing list