>Model: 850 Evo 500 GB SATA III 6Gb/s - please check the SSD *"DRIVE HEALTH STATUS"* and the* "S.M.A.R.T values of specified disk" * .... for example - with the "smartctl" tool ( https://www.smartmontools.org/ ) ( -x "Show all information for device" ) Expected output with "Samsung SSD 850 EVO 500GB" https://superuser.com/questions/1169810/smart-data-of-a-new-ssd
Regards, Imre Neto pr <neto...@gmail.com> ezt írta (időpont: 2018. júl. 18., Sze, 3:17): > 2018-07-17 22:13 GMT-03:00 Neto pr <neto...@gmail.com>: > > 2018-07-17 20:04 GMT-03:00 Mark Kirkwood <mark.kirkw...@catalyst.net.nz > >: > >> Ok, so dropping the cache is good. > >> > >> How are you ensuring that you have one test setup on the HDDs and one > on the > >> SSDs? i.e do you have 2 postgres instances? or are you using one > instance > >> with tablespaces to locate the relevant tables? If the 2nd case then you > >> will get pollution of shared_buffers if you don't restart between the > HHD > >> and SSD tests. If you have 2 instances then you need to carefully check > the > >> parameters are set the same (and probably shut the HDD instance down > when > >> testing the SSD etc). > >> > > Dear Mark > > To ensure that the test is honest and has the same configuration the > > O.S. and also DBMS, my O.S. is installed on the SSD and DBMS as well. > > I have an instance only of DBMS and two database. > > - a database called tpch40gnorhdd with tablespace on the HDD disk. > > - a database called tpch40gnorssd with tablespace on the SSD disk. > > See below: > > > > postgres=# \l > > List of databases > > Name | Owner | Encoding | Collate | Ctype | > > Access privileges > > > ---------------+----------+----------+-------------+-------------+----------------------- > > postgres | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | > > template0 | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | > > =c/postgres + > > | | | | | > > postgres=CTc/postgres > > template1 | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 | > > =c/postgres + > > | | | | | > > postgres=CTc/postgres > > tpch40gnorhdd | user1 | UTF8 | en_US.UTF-8 | en_US.UTF-8 | > > tpch40gnorssd | user1 | UTF8 | en_US.UTF-8 | en_US.UTF-8 | > > (5 rows) > > > > postgres=# > > > > After 7 query execution in a database tpch40gnorhdd I restart the DBMS > > (/etc/init.d/pg101norssd restart and drop cache of the O.S.) and go to > > execution test with the database tpch40gnorssd. > > You think in this case there is pollution of shared_buffers? > > Why do you think having O.S. on SSD is bad? Do you could explain better? > > > > Best regards > > []`s Neto > > > > +1 information about EVO SSD Samsung: > > Model: 850 Evo 500 GB SATA III 6Gb/s - > http://www.samsung.com/semiconductor/minisite/ssd/product/consumer/850evo/ > > > >> I can see a couple of things in your setup that might pessimize the SDD > >> case: > >> - you have OS on the SSD - if you tests make the system swap then this > will > >> wreck the SSD result > >> - you have RAID 0 SSD...some of the cheaper ones slow down when you do > this. > >> maybe test with a single SSD > >> > >> regards > >> Mark > >> > >> On 18/07/18 01:04, Neto pr wrote (note snippage): > >> > >>> (echo 3> / proc / sys / vm / drop_caches; > >>> > >>> discs: > >>> - 2 units of Samsung Evo SSD 500 GB (mounted on ZERO RAID) > >>> - 2 SATA 7500 Krpm HDD units - 1TB (mounted on ZERO RAID) > >>> > >>> - The Operating System and the Postgresql DBMS are installed on the SSD > >>> disk. > >>> > >>> > >> > >
