If you're talking about PostgreSQL, the general consensus from the mailing lists and IRC discussions seems to be that you should in fact not put your WAL on SSDs. $PGDATA/base, yes; $PGDATA/pg_xlog, no.
The amount of write churn in your WAL will burn through your SSDs wear leveling very quickly, and given that WAL is nearly perfectly sequential in access pattern, you lose (forfeit) nearly all the random IO benefit an SSD buys you.
My production master/slave pair only have SSD in them, so I'm "doing this wrong", given that advice. Our SSDs are SLC NAND, however, so their write endurance is vastly, vastly higher than the drives under consideration in both your comment, and TFA.
If you're talking about PostgreSQL, the general consensus from the mailing lists and IRC discussions seems to be that you should in fact not put your WAL on SSDs. $PGDATA/base, yes; $PGDATA/pg_xlog, no.
The amount of write churn in your WAL will burn through your SSDs wear leveling very quickly, and given that WAL is nearly perfectly sequential in access pattern, you lose (forfeit) nearly all the random IO benefit an SSD buys you.
My production master/slave pair only have SSD in them, so I'm "doing this wrong", given that advice. Our SSDs are SLC NAND, however, so their write endurance is vastly, vastly higher than the drives under consideration in both your comment, and TFA.