Re: Amazon High I/O instances
От | Sébastien Lorion |
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Тема | Re: Amazon High I/O instances |
Дата | |
Msg-id | CAGa5y0OpZy6fTPvrO-t2QfUqoEzjpHqqPO7G+3k8NB3eHeSYXA@mail.gmail.com обсуждение исходный текст |
Ответ на | Re: Amazon High I/O instances (John R Pierce <pierce@hogranch.com>) |
Список | pgsql-general |
I will be setting up an instance in the coming days and post the results here.
While reading on the subject, I found this interesting discussion on YCombinator:
Sébastien
On Thu, Aug 23, 2012 at 2:41 PM, John R Pierce <pierce@hogranch.com> wrote:
On 08/23/12 11:24 AM, Sébastien Lorion wrote:I don't use AWS at all. But, it shouldnt take more than a couple hours to spin up an instance, populate a pgbench database and run a series of pgbench runs against it, and do the same against any other sort of system you wish to use as your reference.I think both kind of tests (general and app specific) are complementary and useful in their own way. At a minimum, if the general ones fail, why go to the expenses of doing the specific ones ? Setting up a meaningful application test can take a lot of time and it can be hard to pinpoint exactly where in the stack the performance drops occur. The way I see it, synthetic benchmarks allow to isolate somewhat the layers and serve as a base to validate application tests done later on. It surprises me that asking for the general perf behavior of a platform is controversial.
I like to test with a database about twice the size of the available memory if I'm testing IO, and I've found that pgbench -i -s ####, for ####=10000 it generates a 1 billion row table and uses about 150GB (and a hour or so to initialize on fast IO hardware). I then run pgbench with -c of about 2-4X the cpu/thread count, and -j of about -c/16, and a -t of at least 10000 (so each client connection runs 10000 transactions).
on a modest but decent 2U class 2-socket dedicated server with a decent raid card and raid10 across enough spindles, I can see numbers as high as 5000 transactions/second with 15krpm rust, and 7000-8000 with a couple MLC SSD's striped. trying to raid10 a bunch of SATA 7200 disks gives numbers more like 1000. using host based raid, without a write-back cache in the raid card, gives numbers about 1/2 the above. the IOPS during these tests hit around 12000 or 15000 small writes/second.
doing this level of IO on a midsized SAN can often cause the SAN CPU to run at 80%+ so if there's other activity on the SAN from other hosts, good luck.
in a heavily virtualized shared-everything environment, I'm guessing your numbers will be all over the place and difficult to achieve consistency.
--
john r pierce N 37, W 122
santa cruz ca mid-left coast
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