[AlisdairO]

I'm really not sure you read my post very thoroughly. I'm fairly intimately acquainted with the internals of database systems, and you don't seem to be replying to what I actually wrote - I wasn't attacking your point of view (I generally agree that a decently designed DB is unlikely to trash an SSD all that quickly), I was just hoping to shed light on the other poster's wording.

If you have an 8kb block and you change 128 bytes of it, the 'actual update' is much smaller than 8kb. Sure, you're reading/writing 8kb to disk, but everything outside of that 128 bytes is basically fat for the purposes of that change. As I said in my previous post, that can absolutely be mitigated by writes being combined through the checkpointing process, and one would hope that a decent SSD could cope easily with combining writes to an appending log.

A database can still be writing data all over the place. A heavily indexed table can cause quite varied write patterns, which can result in a lot of different pages getting touched. Fortunately, the reality is that well-designed DBs and SSDs are fairly capable of dealing with this.

[engendered]

My original comment on this whole discussion was that few databases write more than 100GB a day. I am not talking about whether you inserted n integers or updated so many varchar columns -- when you actually monitor its IO, it is extremely unlikely that your database exceeds 100GB a day of writes, and in all likelihood is a magnitude or two below this. Whenever anyone waves their hands and talks about databases as if they somehow imply massive use, they're just fearmongering -- actual empirical stats are your friend, and actual empirical stats show that most real-world databases barely register on the lifespan of most SSDs.

So now that we're in an understanding that we're talking about database writes to IO, the other matter is how it writes it. I've built a lot of systems on a lot of databases, and the write amplification has generally been very low. I've been building and running significant databases on SSDs for about 7 years now, and while everyone else is finally starting to realize that they're wasting their time if they aren't, we still see the sort of extreme niche fearmongering that makes other people clutch onto their magnetic storage (and I heard it the entire time. "OMG but don't databases kill flash???!?!?". No, certain volumes of writes and types of writes do. Only metering will tell you if that applies). Yes, some people do very odd things that can kill storage, but that is extremely rare. It almost certainly doesn't apply to the overwhelming percentage of HN readers.