3 ms·

From my experience I/O is more important than CPU for DB, I've never seen the 24 cores of our servers having problems, however the raid 10...

• justinsb 12y ago
  It really depends on your workload. If your working-set fits into memory and is read-mostly, your I/O is basically irrelevant. Even if you're not in-memory, if you are doing mostly sequential reads (like the OLAP queries they are benchmarking), each drive can do ~200MB/second, so it is not too difficult to become CPU bound if you are doing any significant processing on each row (particularly if your row size is small!) For OLTP queries, particularly with working-set > RAM or lots of writes, your disk I/O is probably the bottleneck (probably your IOPS, actually, which is why SSD can be so valuable). Pretty sure they're not targeting that use-case though!
  • swasheck 12y ago
    in my experience (which isn't the sum-total of all human experience), our OLAP queries have a bottleneck at the fiber interconnect between the storage controller and the OS. cpu still isn't the problem for our OLAP systems. your point that great strides have been made in storage such that we could be back at cpu as a bottleneck is well taken though.
• jcampbell1 12y ago
  I assume you are using cheap spinning disks, and not something like a fusion-io drive. How big is your dataset?
  • swasheck 12y ago
    that's a narrow assumption. why not get more information from the person instead of simply attacking a straw man.
    • jcampbell1 12y ago
      It is a reasonable assumption given he said "raid 10". By "cheap" I mean all spinning disks. Enterprise SSDs are an order of magnitude more expensive than the best spinning platters. ~$25k for 3TB.
      • swasheck 12y ago
        not sure why i was downvoted, but oh well. really? you don't RAID your SSDs?
        • nl 12y ago
          Raid 10 basically just gives performance over Raid 1. You might Raid 1 SSDs but Raid 10 is likely to be a very expensive way to hit your IO bus limits. Given that, assuming it is spinning disk is a reasonable assumption, and the accusation of a strawman was unnecessarily rude.
          • swasheck 12y ago
            I don't find it to be unnecessarily rude. It was a legitimate critique of the poster's own assumptions. I guess that because I'm not an HN "insider" I'm not allowed to challenge someone's assumptions. Only once you hit the magical karma level are you able to do such things.