Will 6Gb/s SAS make a difference for you?

[#1]

Some of you read my post on drive performance, 'How fast are your drives?,' and have wondered if investing in a 6Gb/s SAS storage infrastructure makes sense for your environment.  Traditional SAS systems have a transfer rate of 3Gb/s, so the new HP 6Gb/s SAS drives and Smart Array controllers have doubled the available bandwidth of storage subsystems.

Given that 6Gb/s refers to the system throughput or the speed at which data travels among the components of the storage subsystem (the drive, controller, server backplane, and/or SAS expander and JBOD), will your system performance really improve?  Well, if your environment consists of a small number of storage devices and your I/O workload is 40% or less, you probably won't see any benefits beyond generational improvements (e.g. performance and technology improvements that happen over time).  In such environments, the bottleneck may actually be the speed at which bits can be moved to (from) the hard disk platters from (to) the hard disk's integrated controller and the fast transfer among storage devices may be "wasted."

However, if you're running multi-device, storage-intensive applications, such as video streaming, server virtualization, or real-time backup systems, you'll want to make sure your system doesn't saturate as often and pumping data through the system faster will help keep up with your heavy I/O demands.

If you're running a ProLiant G6 server and have a 6Gb/s SAS storage infrastructure, let's hear what kind of application you're running.

[#2]

I'm trying to find 6Gb SAS controllers on the HP web server, ala a P800 like device that can go 6Gb vs. the 3Gb of the P800, is there one?  Also, I see some of the raw drive capacities (300, 450, 600GB / 15k) that have 6Gb interface variants, but are all the rest of the pieces available yet to make a complete PCI-E bus to disk connection?

thank you,

Dave

[#3]

The 6Gb/s SAS version of the P800 will launch in early 2010.

S. Mathur

[#4]

Hello,

I'm using a RAID 5 configuration, so please keep this in mind for the below.

From what I understand, a spinning hard drive (vs. SSD) will never hit anywhere near the limit for 3G speed for sustained read/writes.

1) Is there any reason to get 6G spinning hard drives, and if so, in what situations and why?

From what I can gather, and these are rough numbers, a SAS 10K drive can push out a sustained 88MB/sec/drive, and a SAS 15K drive can do about 120MB/sec/drive.

If a 3G controller can maintain it's theoretical 3G throughput (doubtful), then I would need at least four SAS 10K drives or three 15K SAS drives before I could possibly see any real benefit to 6G.

2) Is this logic flawed, and if so, how?

3) What is the maximum sustained throughput on a 6G controller, e.g., the HP P410 (462862-B21)?

4) In what situations does it make sense to use a 6G controller with 3G drives?

I have been asking all sorts of HP people and nobody seems to be able to answer these, so any help would be appreciated.

Many thanks.