INSERT - UPDATE throughput oscillating and SSD activity after stopping the client

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От Tom DalPozzo
Тема INSERT - UPDATE throughput oscillating and SSD activity after stopping the client
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Msg-id CAK77FCTVTyCNn=8CZbZUMDiWnZKyioFCJFzTY_ZiywSLCxEk-w@mail.gmail.com
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Ответы Re: INSERT - UPDATE throughput oscillating and SSD activity after stopping the client
Re: INSERT - UPDATE throughput oscillating and SSD activity after stopping the client
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Hi,
I've two tables, t1 and t2, both with one bigint id indexed field and one 256 char data field; t1 has always got 10000 row, while t2 is increasing as explained in the following.

My pqlib client countinously updates  one row in t1 (every time targeting a different row) and inserts a new row in t2. All this in blocks of 1000 update-insert per commit, in order to get better performance.
Wal_method is fsync, fsync is on, attached my conf file. 
I've a 3.8ghz laptop with evo SSD.

Performance is  measured every two executed blocks and related to these blocks.

Over the first few minutes performance is around 10Krow/s then it slowly drops, over next few minutes to 4Krow/s, then it slowly returns high and so on, like a wave.
I don't understand this behaviour. Is it normal? What does it depend on?

Also, when I stop the client I see the SSD light still heavily working. It would last quite a while unless I stop the postgresql server, in this case it suddenly stops. If I restart the server it remains off.
I'm wondering if it's normal. I'd like to be sure that my data are safe once commited.

Regards
Pupillo

P.S.: I put this question in general questions as my concern is not if the performance is high or not.









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