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Re: MySQL with SSD/HDD
Posted by: Rick James
Date: February 11, 2014 08:26PM

> I would use the SDD for all innoDB data except for Redo log and ibdata, which I would put on HDD.

Not quite. Logs, in general, should be on HDD, because they tend to be accessed sequentially, not randomly.

ibdata1, regardless of the value of innodb_file_per_table (which should be 1), should be on SSD. Also .ibd files.

So, you may as well put most of the mysql tree on SSD.

Do SHOW VARIABLES LIKE 'innodb%';
There are several settings that should be increased. (The values default to HDD values.) These two come to mind:
innodb_flush_neighbors = OFF
innodb_io_capacity = 2000
There may be more.

> will performance be better if the OS is installed on SSD?

One can hope that the OS is not doing any I/O after starting up.
There should be no swapping. (If there is, that will be really bad.)

> since our InnoDB database size (75GB) exceeds the RAM size (32GB), we plan to use SSD drives
> innodb_buffer_pool_size = 26624M

That may be overkill. If your "working set" is less than 26GB, then the extra I/O speed will go unused. Also, there are _usually_ ways to improve performance without using hardware -- better indexes, batching INSERTs, rewriting SELECTs, normalizing, denormalizing, summary tables, etc.

If you have the money, switch to SSDs. If you want to be frugal, let's see the schema and queries.

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