On a RAID-5 array of 4x SAS disks, turning the sync off made it about 2x faster, give or take.
On the "SSD", it was about 150x faster. Is the only change the absence of a call to "fsync()" when turning synchronous off? If so, I can conclusively say that fsync() is very slow on this storage device. Thanks for the suggestion. Mark Pavel Ivanov wrote: > If you execute > > pragma synchronous = off; > > you'll be able to compare performance with syncs and without them. So > if you make this comparison on standard spinning disk and on SSD > you'll see if syncs on SSD indeed extra-ordinary slow. > > Pavel > > On Wed, Sep 23, 2009 at 10:09 AM, Mark <godef...@gmail.com> wrote: >> It's very possible, but I don't know how to tell. Is there an easy way >> to know if the sync() calls are taking inordinately long? >> >> Mark >> >> >> Thomas Briggs wrote: >>> Is the sync necessary to commit a transaction slow? Performance of >>> that sync depends on the OS, file system, hardwar, etc. IIRC, so IOs >>> may be fast but it's possible that the syncs are killing you. >>> >>> -T >>> >>> On Tue, Sep 22, 2009 at 5:14 PM, Mark <godef...@gmail.com> wrote: >>>> Lothar Scholz wrote: >>>>> Hello Mark, >>>>> >>>>> Tuesday, September 22, 2009, 3:53:48 AM, you wrote: >>>>> >>>>> M> I've currently got a loaner high-performance flash-based "SSD" (let's >>>>> M> just say it doesn't connect to any disk controllers) that I'm testing >>>>> M> for performance. I've run my application against it, and I believe that >>>>> M> I should see numbers MUCH higher than I do. When I run my test app on a >>>>> M> normal SATA 7200 RPM disk, I get a certain performance, and on the >>>>> "SSD" >>>>> M> I get about 1/10th that speed. On an array of SAS disks I get numbers >>>>> M> that are about 5x faster than my SATA disk, so my software itself isn't >>>>> M> (I believe) the bottleneck. >>>>> >>>>> M> I'm wondering if anyone has any tips for "optimizing" for this sort of >>>>> M> storage solution. >>>>> >>>>> Throw it into the trash bin and buy a new one which has a 3rd >>>>> generation controller and at least 64MB fast cache. The old JMicron >>>>> controller that many low cost SSD still use was developed for Flash >>>>> USB sticks. >>>>> >>>>> With modern SSD like the latest Samsung should give you at least the >>>>> same performance as the SATA. If it gets better depends on file size >>>>> and cache. Are you sure that the SAS RAID Controller is not keeping >>>>> everything in the controller cache? >>>> This isn't an "SSD". It's connected directly to the PCI Express bus, and >>>> "low cost" it certainly is NOT. It's much more valuable than the server >>>> it's plugged into. >>>> >>>> I've run benchmark tests (iometer), and the benchmarks show it's as fast >>>> as the mfgr says it should be (~700MB/sec read and write bandwidth, >>>> >115,000 IOPS) but it performs quite poorly when I run my app on it. I >>>> can't figure out why. >>>> >>>> Mark _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
