[ZODB-Dev] Using zodb and blobs

[Jim Fulton]

On Tue, Apr 13, 2010 at 8:42 PM, Nitro <nitro at dr-code.org> wrote:
> Am 14.04.2010, 04:08 Uhr, schrieb Laurence Rowe <l at lrowe.co.uk>:
>
>> Running your test script on my small amazon EC2 instance on linux
>> takes between 0.0 and 0.04 seconds (I had to remove the divide by
>> total to avoid a zero division error). 0.02 is 5000/s.
>
> I don't know how EC2 works in detail, but 5000 transactions per second
> sound impossible to write to disk. Even 500 are impossible if your disk
> doesn't have VERY fast access times.

Unlike most other databases, ZODB records written to file storages are always
appended, so there is no seeking involved.  The only seeking involved in writes
is that needed to read previous records, but if a test is simply
writing the same
object over and over, or updating a small corpus, the previous record is likely
to be in disk cache. Of course, other things happening on the system will
typically cause the disk heads to seek away from the end of the database file,
but you're unlikely to see that in a simpler benchmark.

Jim

-- 
Jim Fulton