|
Seriously, if performance under heavy load is critical to your application the vast majority of all your operations has to occur in memory. SSD gives you a buffer, but under random access load, disks just won't keep up.
I'll have to read your link, but SQL Server needs more than just the storage database in memory, It's got to have all of the temp and system databases as well or paging can become an issue.
|
|
|
|
|
Their memory is more than disk space on some of the machines I get to work with. Feeling depressed. Need alcohol.
|
|
|
|
|
not-enough-hampsters
B
MCAD
---
|
|
|
|
|
They've got it![^]
It's an OO world.
public class SanderRossel : Lazy<Person>
{
public void DoWork()
{
throw new NotSupportedException();
}
}
|
|
|
|
|
This is a fairly common technique. Most banks offer similar setups.
|
|
|
|
|
Nish Sivakumar wrote: The entire database is cached in-memory. The entire thing.
Calm down, it's virtual memory.
THESE PEOPLE REALLY BOTHER ME!! How can they know what you should do without knowing what you want done?!?!
-- C++ FQA Lite
|
|
|
|
|
Sounds like physical memory to me:
>> With their SQL Servers loaded with 384 GB of RAM and 2TB of SSD...
Or is there another definition of virtual memory in DB land I'm unaware of?
|
|
|
|
|
Yes, it is. I was kidding.
THESE PEOPLE REALLY BOTHER ME!! How can they know what you should do without knowing what you want done?!?!
-- C++ FQA Lite
|
|
|
|
|
Sorry - I couldn't make sense of the contradiction even with your 'awe shucks', and it left me puzzled.
|
|
|
|
|
CPallini has always told us that he's Italy's funniest programmer. The rest of us have yet to see any truth in that.
|
|
|
|
|
Evidently he is a very brave man, having boldly gone a level of indirection deeper into humor then any of his countrymen. A giant in his shoes - I stand corrected. Thank you.
|
|
|
|
|
Nish Sivakumar wrote: CPallini has always told us that he's Italy's funniest programmer.
They held a contest?
A positive attitude may not solve every problem, but it will annoy enough people to be worth the effort.
|
|
|
|
|
Nish Sivakumar wrote: The entire database is cached in-memory. The entire thing
Yep - in fact there are database systems that are designed to work in that mode. I am working on one: SAP HANA[^]
|
|
|
|
|
That sounds neat. So these in-memory databases, they would keep persisting to a more solid storage source periodically, correct?
|
|
|
|
|
I would assume so. Back many years ago, I worked on some VAX/VMS systems where we had files mapped to memory for performance. Periodically, they would be 'flushed' back to the drives.
It wasn't as robust as a database system, but the concept was the same. The systems we used were integrated and could recover from a unexpected outage where data was lost.
|
|
|
|
|
SQL server added optimized in memory tables for SQL 2014. SQL server ends up generating C code, and then fires up a compiler behind the scenes to generate the access and indexing code. That's probably a step beyond what stack overflow is doing, but the performance improvement can be huge, especially switching from disk optimized data structures like b-trees to hash tables. It's not necessarily about the storage, but the optimizations you can do knowing that you never have to hit disk for a lookup.
edit, added a link: http://msdn.microsoft.com/en-us/library/dn133165.aspx[^]
|
|
|
|
|
Cool - interesting stuff there!
|
|
|
|
|
Nish Sivakumar wrote: So these in-memory databases, they would keep persisting to a more solid storage
source periodically, correct?
Correct. Here is the architecture of SAP HANA[^] and you can see the Persistence layer which is responsible for (re)storing data to and from disk.
|
|
|
|
|
|
ME: Wanna see Guardians of the Galaxy on August 2nd?
WIFE: What is it about?
ME: Uhhh... it is... uh... it is set in 19th Century England and it is a story about class struggle... and ... er.. .love and it stars, eh... Nicole Kidman, Hugh Grant and it is directed by Kenneth Branagh.
WIFE: Sure, I'll go.
|
|
|
|
|
MehGerbil wrote: August 2nd
Headlines Aug 3rd
A man was brutally slain by his enraged wife when she discovered that he lied to her about the movie being a chick flick. Film at 11.
|
|
|
|
|
|
Oddly enough, that news report sounds more interesting then the movies she drags me to...
|
|
|
|
|
You not none of these people who feel agoraphobic when you are not in the dog box..
|
|
|
|
|
If your wife is smart, she'll just smile and wait. The time will come when she takes you to a movie, taking away all sharp instruments and rope and make you sit through it. Something like Twilight, only worse.
|
|
|
|