Scott Marlowe pisze:
>>> So still I don't get this: select * from table; on old server takes 0,5 sec,
>>> on new one takes 6sec. Why there is so big difference? And it does not
>>> matter how good or bad select is to measure performance, because I don't
>>> measure the performance, I measure the relative difference. Somwhere there
>>> is a bottleneck.
>> Yep, the network I'd say. How fast are things like scp between the
>> various machines?
Sure it is, but not in a way one could expect:
- scp from 1000Gbit laptop to old server 27MB/sec
- scp from the same laptop to new server 70MB/sec
Both servers have 1000Gbit connection. So it is still mysterious why old
server makes 9x faster select?
I don't claim that something is slow on new (or even older) server. Not
at all. the application works fine (still on older machine). I only
wonder about those differences.
>>> 4. Machine. The new server has 5 SAS disks (+ 1 spare), but I don't remember
>>> how they are set up now (looks like mirror for system '/' and RAID5 for rest
>>> - including DB). size of the DB is 405MB
>> Get off of RAID-5 if possible. A 3 Disk RAID-5 is the slowest
>> possible combination for RAID-5 and RAID-5 is generally the poorest
>> choice for a db server.
Sure I know that RAID-5 is slower than mirror but anyway how much
slower? And for sure not as much as single ATA disk.
> I refer you to this classic post on the subject:
> http://www.mail-archive.com/pgsql-general@postgresql.org/msg93043.html
Well, this thread is about benchmarking databases (or even worse,
comparison between two RDBMS). I'm not benchmarking anything, just
compare one factor.
P.