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Re: slow queries and high % of wait I/O
Posted by: jawahar Muthukrishnan
Date: January 20, 2009 12:50PM

Increasing RAM ( a short-term strategy)
a. The production server "ibdata" file size is approximately 13GB. One line of thought in our group is that if we increase the RAM to 16 GB (it is currently 8GB), then OS file cache should load the entire file in memory and it should help us for the short-term by reducing disk I/O (atleast SELECTS will not require disk reads all the time)... Could you please comment if this will really work?

Long-term strategy:
b. Since we need to read all 25 records for each device_id, we are thinking of storing all the records as BLOB (indexed by device_id).

schema change will be as follows:
create table history (
id int auto_increment,
device_id VARCHAR,
history longBLOB // we will store a serialized object
)

So, instead of 25 disk seeks, this will probably be only 1. Is this a good strategy as our use case DOES NOT require us to search on any of the fields on the table other than deviceid? How does BLOB behave with repeated updates, since it is our use case?



Edited 2 time(s). Last edit at 01/20/2009 11:40PM by jawahar Muthukrishnan.

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