la·ten·cy – Computers . the time required to locate the first bit or character in a storage location, expressed as access timeminus word time.
Often when talking to people about performance they get rapped around the MB/Sec number and ignore a critical factor, latency. SQL Server is one of those few applications that is very sensitive to disk and network latency. Latency is what the end user sees. If your SQL Server is waiting around for disk or network they will start to complain. In an OLTP environment SQL Server accesses data on More >
I attended and spoke at SQLSaturday #57, and it was an awesome event! Here are my notes and observations on the trip as a whole.
As always, I try to be in town on Friday night to do the speaker dinner. It’s always worth it. Even if you hate the food, resturant or the part of town the PEOPLE make it so worth wild. I always meet someone new and get to cultivate relationships that normally would only get some TLC at The Summit. To me SQLSaturday is a cheap way to keep my speaking skills sharp, educate some folks and get to spend quality time with a great group of people.
Friday night I got to do More >
We are in the final stages of selecting the speakers for the SQLRally May 11th through the 13th in sunny Orlando Florida. The program selection is a little different than what we have done with the Summit. The committee narrowed the number of selections and is putting the rest up to a public vote. This is your opportunity to voice your opinion on what you would like to hear at this inaugural event! I’ve been fortunate enough to have two of my sessions put up for a vote. If you follow my blog you know I have a passion for moving bits of data around as fast as possible. Both my sessions focus More >
I recently wrote about solid state storage and its different form factor. Well, several major manufacturers have realized that solid state needs all the bandwidth it can get. Dell, IBM, EMC, Fujitsu and Intel have formed the SSD Form Factor Working Group bringing PCIe 3 to the same form factor that SATA and SAS use. Focusing on the same connector types and a 2.5” dive housing. I’m not sure how quickly it will make it’s way into the enterprise space but that is clearly it’s target. Reusing the physical form factor cuts down on manufacturing and R&D costs for all involved. They have an More >
If you have been following this series we have covered system buses, hard disks, host bus adapters and RAID. Along the way we also covered how to capture your IO patterns and the SQLIO tool. Now we will pull it all together.We move up the stack even further to the actual layout of the RAID stripe and the file system. How the stripe and file system are laid out on your disks has a huge impact on performance. One of the things that has really gotten some traction over the last few years is sector alignment. This one thing, if not done, could cost you 30% to 40% of your IO potential. Jimmy May More >
In previous articles, we have covered the system bus, host bus adapters, and disk drives. Now we will move up the food chain at take a look at getting several disks to operate as one.
In 1988 David A. Patterson, Garth Gibson, and Randy H. Katz authored a seminal paper, A Case for Redundant Arrays of Inexpensive Disks (RAID). The main concept was to use off the shelf commodity hardware to provide better performance and reliability and a much lower price point than the current generation of storage. Even in 1988, we already knew that CPUs and memory were outpacing disk drives. To try to solve More >
We have covered the Hard Disk and the System Bus. This time around we will cover disk controllers and host bus adapters.In The Beginning…
There were three distinct components to your IO subsystem, the disk, controller, and the host bus adapter. Today there are still three distinct components but the arrangement has changed. The physical disk we have covered and you know about. What you may not realize is the disk controller is actually the circuit board on the back of the hard drive. In the past this board may have been an add-in card, a back plane that the drives plugged into or even an More >
12/03/2009 – UPDATE! There were a couple of bugs in the SQLIOCommandGenerator new SQLIOTools.zip has been updated.
I often tell people one of the greatest things about SQL Server is that anyone can install it. I also tell people what the worst things about SQL Server is that anyone can install it. Microsoft fostered a “black-box” approach to SQL Server in 7.0 and 2000. Thankfully, they are reversing this course. As a follow-on to my last article, capturing I/O patterns, we will take a quick look at building some synthetic tests based on those results. There are several tools on the market More >
As promised and update on what has happened so far. A correction needs to be made. the P800 is a PCIe 1.0 card so the bandwidth is cut in half from 4GB/sec to 2GB/sec.
My CDW rep did get me in contact with an HP technical rep who actually knew something about the hardware in question and its capabilities. It was one of those good news, bad news situations. We will start with the bad news. The performance isn’t off. My worst fears were confirmed.The Hard Disks
The HP Guy (changing the names to protect the innocent) told me their rule of thumb for the performance of the 2.5” 73GB 15K drives More >
This installment we will cover what connects the controller to the computer.
Disk controllers use a system bus to talk to your CPU and memory. It also determines the maximum speed your disk can talk to the computer. There may be as many as six different system busses in your computer. We are only interested in the ones that directly connect your disk controllers.
The oldest bus still in general use is PCI. You can still find them in your desktop and in servers though it is really on the way out. We are only covering PCI 2.0 32 bits wide running at 33 MHz. This allows for a theoretical top More >