6 ms·

Here's a better trick - treat a database as an indexed storage layer that's doing the minimum of CPU work or complicated transactional conditions that create lo

by jbooth 16y ago

Here's a better trick - treat a database as an indexed storage layer that's doing the minimum of CPU work or complicated transactional conditions that create lots of blocking and bottleneck conditions for threads on your monolithic back end. And then implement the app logic in some slow-ass web language that doesn't hold a candle to your database's optimized C. What happens when your web server can't keep up? Buy another web server. That's an easily solvable problem. A saturated DB, on the other hand, is very hard to fix, especially if all of your application logic is running in it and would require a rewrite to scale.

gaius 16y ago
There's an awful lot more to computing than websites. FWIW I work on a "non-scalable" RDBMS that comfortably handles thousands of commits/sec, tens of thousands of selects/sec and tens of terabytes of data. All done with stored procs, one database, no need for "sharding" either. Will it scale indefinitely? No, but neither will anything else. The limits of the RDBMS are orders of magnitude greater than the NoSQL crowd think they are.
- mmt 16y ago
  The limits of the RDBMS are orders of magnitude greater than the NoSQL crowd think they are. Agreed. There's a couple of orders of magnitude just from I/O improvement in hardware, using conventional[1] hardware, configured intelligently. There's at least another order of magnitude in optimizations that aren't possible in NoSQL's strawman[2], such as separate tablespaces for data and index, partial indexes, and a galaxy of query tuning from an EXPLAIN that actuall provides a query plan. [1] Meaning commodity-priced, nothing fancier than $400 RAID cards and spinning disks. [2] MySQL
  - jbooth 16y ago
    There is nothing approaching even a single order of magnitude in improvement in random I/O with conventional HDDs over the last, say, 20 years. Not even a 2X improvement. You're under 500 IOPS per HDD, period, use them wisely. Moore's law doesn't apply to RPMs of spinning disks.
    - mmt 16y ago
      You're under 500 IOPS per HDD, period This is only significant if one is limited to a trivial number of spinning disks. 20 years ago, with separate disk controllers, this was the case. If you run some benchmarks, I expect you'll find that, for random I/O, N disks perform better than N times one of those disks. SCSI provided (arguably) an order of magnitude for number of disks per system. Now, SAS provides another. $8k will buy 100 disks (and enclosures, expanders, etc). How many IOPS is that? ETA: The Fujitsu Eagle (my archetype of 20ish years ago disk technology) had, IIRC, an average access time of 28ms. If its sequential transfer rate was one 60-100th of modern disks, what fraction of a modern disk's 4k IOPS could it do?
      - jbooth 16y ago
        Yes, I agree that the solution is to throw more spindles at the problem. PL/SQL, though, with global data reach and advanced locking states for every single transaction, make it really hard to move off of a single host. So it's more and more work to get more disks attached to that host, and CPU is a hard upper limit.
    - fleitz 16y ago
      Yes, but a battery backed write cache will turn random IO into sequential IO eliminating this '500 IOPS' barrier. Put 512 MB of BBWC into a system and see how your 'random IO' performs. The whole point is that NO ONE scans their ENTIRE dataset randomly, if you have to scan your entire dataset, just access it sequentially. Plus, nothing in NoSQL solves ANY of the points you are outlining.
      - jbooth 16y ago
        Write cache is useful of course but it doesn't make random reads any faster. If your dataset is too big to cache, disk latency becomes your limiting factor. The question then becomes how to most effectively deploy as many spindles as possible in your solution - SANs are one way, sharding/distribution across multiple nodes another.
        16y ago
  - silentbicycle 16y ago
    In discussions about "NoSQL" systems, I've found out that some of the developers complaining about RDBMS performance didn't even know what indexes were. Usually they learned how to use MySQL from thirdhand PHP & MySQL tutorials off somebody's blog or something, and thought it was representative of all RDBMSs. Not saying everyone using "NoSQL" is poorly informed, just that sometimes peoples' impressions of performance aren't very accurate. It makes me suspicious when somebody's benchmark only uses MySQL.
    - SkyMarshal 16y ago
      I've slowly come to the same opinion over the past few years. I'm just going to leave this here for posterity: http://www.dbdebunk.com/ http://www.dbdebunk.com/
- jbooth 16y ago
  SSDs? A HDD is limited to well under a thousand reads per second, and there's multiple reads per SQL select, so I'll assume either yes or you're leaving something out. If the tens of thousands of reads are over a 4MB table that stays in memory and the rest of your 10TB are infrequently accessed, congrats, you have a single-node problem. If you actually need to deliver, say, 1,000 queries per second over a 10TB dataset? It's not happening in an RDBMS unless you get a whole bunch of SSDs. Also, RE: websites, of course, substitute your environment's front end if you'd like.
  - ora600 16y ago
    Its year 2010, we've invented RAID a while back. Stripe and mirror everything and you get decent performance without SSD.
    - jbooth 16y ago
      Ok, you're up to 3k random reads per second at the absolute peak. Realistically more like 2k for 6x10k disks at RAID 0, and it's awfully hard to even fit 10TB on a RAID1+0 setup. What's that, 10x2TB? Good luck with the latencies on those 2TB disks. Still doesn't add up to 10k select statements per second over a 10TB dataset on a singlenode. Even without writes, that's not happening. I call BS on grandparent post.
      - CrLf 16y ago
        That shows a lack of understanding of what kind of hardware is being used in the real world to handle this. With a half-decent SAN with 15k drives and 4Gbit fibrechannel connections, you can get 1000+ IOPS without the storage system even breaking a sweat. Under load it can easily give 10 times that. This is something that's everywhere in the business world. Pair this with a bunch of cores and a few GB of memory, and you can have an RDBMS that chews through impressive amounts of data. Unless, of course, you optimize nothing and swamp it with lame queries that do nothing that table scans. Funny enough, the same people that are fine with doing everything in code are the ones that can't be bothered to think more than one second about what kind of queries they are throwing at the database.
- fleitz 16y ago
  Excellent response, it's amazing how many people have never seen a SQL server with 200 disks attached to it, and we're not even talking about SANs. A single quad core chip can easily drive 200 disks. All people see is a $200,000 price tag for a single system and ignore the fact that it will outperform 100 $2000 servers. AMD64 can scale so far these days there is little point to NoSQL for all but the highest end of web-scale. I bet if you look into the core of Google there are still mysql systems doing a lot of grunt work.
  - jbooth 16y ago
    Facebook still has MySQL doing a bunch of grunt work, but they're basically treating it like a NoSQL store - sharded key-value storage and that's it. They're moving to HBase now. And, yeah, damn right I'm hesitant about a single piece of hardware that costs $200k and still leaves you with a SPOF. Effectively you're saying it's a 400k piece of hardware after replication. Oh, and Oracle replication software costs you an extra several hundred thousand. So for about a million dollars, yeah, unless it's incredibly transactional in nature, I'd give other options a very serious look.
    - fleitz 16y ago
      It costs $5k for SQL Server with replication, you can use SQL Express for the monitor so all you're looking at is the 5K license you'd need for SQL Server Standard, if you need Enterprise it's only 20K. This are all retail prices which no one actually pays.
      - jbooth 16y ago
        Ok, and if you have 50GB of data and have made a determination that SQL Server has some features that you're willing to pay 5k for, fine. I still think embedding all your app logic together with your underlying data in PL/SQL or any equivalents is a bad idea but hey that's for anyone to do and find out themselves :)
- SkyMarshal 16y ago
  >All done with stored procs >The limits of the RDBMS are orders of magnitude greater than the NoSQL crowd think they are. Wish I had more upvotes. Knowing what logic to put in stored procs, and what to put in the application code, so as to play to the strengths of the db and the strengths of the appserver, seems to be a lost art these days.
  - jbooth 16y ago
    Coprocessors are in the upcoming releases of both HBase and Cassandra - they'll be back :) It's not that there's anything fundamentally wrong with the relational model, it's that, as formulated, it's really hard to split up into multiple machines.
sp4rki 16y ago
I don't get why you were downvoted, as this is so true. I'd rather throw hardware at a problem, than having to get developers to work on a rewrite on the database level. It's cheaper, easier, and totally not risky in comparison. I've always seen databases as an index storage layer and thought that "outsourcing" the apps job to the database while convenient in a lot of cases, are hell to maintain at scale.
- jbooth 16y ago
  Hey, you got downvoted too. Gave you a bump. Dunno why everyone's taking this so personally. It's like they're personally threatened and their approach is to get angry rather than try and understand.
  - gaius 16y ago
    If I had to guess, I'd say that people are downvoting you because even the MySQL guys who spent the 90s arguing against it have now come around to thinking that foreign keys and transactions and stored procs are good things, and they can't be bothered to engage in the discussion again.
    - jbooth 16y ago
      My beef was PL/SQL and too much of the transactions/storedprocs thing. Foreign keys can be a good thing.
  - sp4rki 16y ago
    ^^ I don't get it either. If someone doesn't agree they might as well say so and give reasons to get a discussion going. Instead we get this "Ohh the article said X so you're wrong, I'll downvote and move along" attitude. I guess people don't appreciate debating anymore.
- ora600 16y ago
  You are paying developers to rewrite features that already exist in the database and you think this is "throwing hardware at the problem"?

by jbooth 16y ago

gaius 16y ago

There's an awful lot more to computing than websites. FWIW I work on a "non-scalable" RDBMS that comfortably handles thousands of commits/sec, tens of thousands of selects/sec and tens of terabytes of data. All done with stored procs, one database, no need for "sharding" either. Will it scale indefinitely? No, but neither will anything else. The limits of the RDBMS are orders of magnitude greater than the NoSQL crowd think they are.

mmt 16y ago
The limits of the RDBMS are orders of magnitude greater than the NoSQL crowd think they are. Agreed. There's a couple of orders of magnitude just from I/O improvement in hardware, using conventional[1] hardware, configured intelligently. There's at least another order of magnitude in optimizations that aren't possible in NoSQL's strawman[2], such as separate tablespaces for data and index, partial indexes, and a galaxy of query tuning from an EXPLAIN that actuall provides a query plan. [1] Meaning commodity-priced, nothing fancier than $400 RAID cards and spinning disks. [2] MySQL
- jbooth 16y ago
  There is nothing approaching even a single order of magnitude in improvement in random I/O with conventional HDDs over the last, say, 20 years. Not even a 2X improvement. You're under 500 IOPS per HDD, period, use them wisely. Moore's law doesn't apply to RPMs of spinning disks.
  - mmt 16y ago
    You're under 500 IOPS per HDD, period This is only significant if one is limited to a trivial number of spinning disks. 20 years ago, with separate disk controllers, this was the case. If you run some benchmarks, I expect you'll find that, for random I/O, N disks perform better than N times one of those disks. SCSI provided (arguably) an order of magnitude for number of disks per system. Now, SAS provides another. $8k will buy 100 disks (and enclosures, expanders, etc). How many IOPS is that? ETA: The Fujitsu Eagle (my archetype of 20ish years ago disk technology) had, IIRC, an average access time of 28ms. If its sequential transfer rate was one 60-100th of modern disks, what fraction of a modern disk's 4k IOPS could it do?
    - jbooth 16y ago
      Yes, I agree that the solution is to throw more spindles at the problem. PL/SQL, though, with global data reach and advanced locking states for every single transaction, make it really hard to move off of a single host. So it's more and more work to get more disks attached to that host, and CPU is a hard upper limit.
  - fleitz 16y ago
    Yes, but a battery backed write cache will turn random IO into sequential IO eliminating this '500 IOPS' barrier. Put 512 MB of BBWC into a system and see how your 'random IO' performs. The whole point is that NO ONE scans their ENTIRE dataset randomly, if you have to scan your entire dataset, just access it sequentially. Plus, nothing in NoSQL solves ANY of the points you are outlining.
    - jbooth 16y ago
      Write cache is useful of course but it doesn't make random reads any faster. If your dataset is too big to cache, disk latency becomes your limiting factor. The question then becomes how to most effectively deploy as many spindles as possible in your solution - SANs are one way, sharding/distribution across multiple nodes another.
      - 16y ago
- silentbicycle 16y ago
  In discussions about "NoSQL" systems, I've found out that some of the developers complaining about RDBMS performance didn't even know what indexes were. Usually they learned how to use MySQL from thirdhand PHP & MySQL tutorials off somebody's blog or something, and thought it was representative of all RDBMSs. Not saying everyone using "NoSQL" is poorly informed, just that sometimes peoples' impressions of performance aren't very accurate. It makes me suspicious when somebody's benchmark only uses MySQL.
  - SkyMarshal 16y ago
    I've slowly come to the same opinion over the past few years. I'm just going to leave this here for posterity: http://www.dbdebunk.com/ http://www.dbdebunk.com/
jbooth 16y ago
SSDs? A HDD is limited to well under a thousand reads per second, and there's multiple reads per SQL select, so I'll assume either yes or you're leaving something out. If the tens of thousands of reads are over a 4MB table that stays in memory and the rest of your 10TB are infrequently accessed, congrats, you have a single-node problem. If you actually need to deliver, say, 1,000 queries per second over a 10TB dataset? It's not happening in an RDBMS unless you get a whole bunch of SSDs. Also, RE: websites, of course, substitute your environment's front end if you'd like.
- ora600 16y ago
  Its year 2010, we've invented RAID a while back. Stripe and mirror everything and you get decent performance without SSD.
  - jbooth 16y ago
    Ok, you're up to 3k random reads per second at the absolute peak. Realistically more like 2k for 6x10k disks at RAID 0, and it's awfully hard to even fit 10TB on a RAID1+0 setup. What's that, 10x2TB? Good luck with the latencies on those 2TB disks. Still doesn't add up to 10k select statements per second over a 10TB dataset on a singlenode. Even without writes, that's not happening. I call BS on grandparent post.
    - CrLf 16y ago
      That shows a lack of understanding of what kind of hardware is being used in the real world to handle this. With a half-decent SAN with 15k drives and 4Gbit fibrechannel connections, you can get 1000+ IOPS without the storage system even breaking a sweat. Under load it can easily give 10 times that. This is something that's everywhere in the business world. Pair this with a bunch of cores and a few GB of memory, and you can have an RDBMS that chews through impressive amounts of data. Unless, of course, you optimize nothing and swamp it with lame queries that do nothing that table scans. Funny enough, the same people that are fine with doing everything in code are the ones that can't be bothered to think more than one second about what kind of queries they are throwing at the database.
fleitz 16y ago
Excellent response, it's amazing how many people have never seen a SQL server with 200 disks attached to it, and we're not even talking about SANs. A single quad core chip can easily drive 200 disks. All people see is a $200,000 price tag for a single system and ignore the fact that it will outperform 100 $2000 servers. AMD64 can scale so far these days there is little point to NoSQL for all but the highest end of web-scale. I bet if you look into the core of Google there are still mysql systems doing a lot of grunt work.
- jbooth 16y ago
  Facebook still has MySQL doing a bunch of grunt work, but they're basically treating it like a NoSQL store - sharded key-value storage and that's it. They're moving to HBase now. And, yeah, damn right I'm hesitant about a single piece of hardware that costs $200k and still leaves you with a SPOF. Effectively you're saying it's a 400k piece of hardware after replication. Oh, and Oracle replication software costs you an extra several hundred thousand. So for about a million dollars, yeah, unless it's incredibly transactional in nature, I'd give other options a very serious look.
  - fleitz 16y ago
    It costs $5k for SQL Server with replication, you can use SQL Express for the monitor so all you're looking at is the 5K license you'd need for SQL Server Standard, if you need Enterprise it's only 20K. This are all retail prices which no one actually pays.
    - jbooth 16y ago
      Ok, and if you have 50GB of data and have made a determination that SQL Server has some features that you're willing to pay 5k for, fine. I still think embedding all your app logic together with your underlying data in PL/SQL or any equivalents is a bad idea but hey that's for anyone to do and find out themselves :)
SkyMarshal 16y ago
>All done with stored procs >The limits of the RDBMS are orders of magnitude greater than the NoSQL crowd think they are. Wish I had more upvotes. Knowing what logic to put in stored procs, and what to put in the application code, so as to play to the strengths of the db and the strengths of the appserver, seems to be a lost art these days.
- jbooth 16y ago
  Coprocessors are in the upcoming releases of both HBase and Cassandra - they'll be back :) It's not that there's anything fundamentally wrong with the relational model, it's that, as formulated, it's really hard to split up into multiple machines.

sp4rki 16y ago

I don't get why you were downvoted, as this is so true. I'd rather throw hardware at a problem, than having to get developers to work on a rewrite on the database level. It's cheaper, easier, and totally not risky in comparison. I've always seen databases as an index storage layer and thought that "outsourcing" the apps job to the database while convenient in a lot of cases, are hell to maintain at scale.

jbooth 16y ago
Hey, you got downvoted too. Gave you a bump. Dunno why everyone's taking this so personally. It's like they're personally threatened and their approach is to get angry rather than try and understand.
- gaius 16y ago
  If I had to guess, I'd say that people are downvoting you because even the MySQL guys who spent the 90s arguing against it have now come around to thinking that foreign keys and transactions and stored procs are good things, and they can't be bothered to engage in the discussion again.
  - jbooth 16y ago
    My beef was PL/SQL and too much of the transactions/storedprocs thing. Foreign keys can be a good thing.
- sp4rki 16y ago
  ^^ I don't get it either. If someone doesn't agree they might as well say so and give reasons to get a discussion going. Instead we get this "Ohh the article said X so you're wrong, I'll downvote and move along" attitude. I guess people don't appreciate debating anymore.
ora600 16y ago
You are paying developers to rewrite features that already exist in the database and you think this is "throwing hardware at the problem"?