SSD vs HDD. Help me choose

If you have a system with similar load profile and it already runs for some extended time under near expected load, you can have a estimate how much writes and reads it is doing, using iostat -th (from the package sysstat):

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           4,8%    0,0%    1,7%    0,5%    0,0%   93,1%

      tps    kB_read/s    kB_wrtn/s    kB_read    kB_wrtn Device
    86,51         1,7M       590,7k       2,9T    1014,8G sda
     3,47        29,5k       734,9k      50,6G       1,2T sdb

and compare that with uptime value:

 10:54:04 up 20 days, 20:26,  1 user,  load average: 2,18, 2,13, 1,94

As you can see, sda on this system reads of around 2.9T/20.8days = 140G per day, and writes of around 48G per day. This value must be compared with desired SSD's datasheet value, TBW, to calculate how long it will endure this particular load.

I am sure your your fears are in vain. I found a cheapest SSD in our local store, it has a TBW value of 70 TB. That SSD will be able to endure that load for 1458 days or slightly less than 4 years. Note, my load is from an office hypervisor, there is some accountancy VM, file server; also we run many test labs there and more.

I mean, it's quite hard to wear out a modern SSD, even cheapest one! It'll likely break earlier by different reason other that expected wear out.

Buy yourself lots of RAM, create a ramdisk (/etc/fstab), and do all compiling, linking, etc there, i.e. in memory.

This is my setup and I am saving gigabytes of the SSD wearing everyday. Another benefit: all file related operations are lightning fast!

Nikita is right. The SSD's will last long enough to out weigh their wear rating. SQL, being such an important structure component, affects so many other systems. I would always suggest getting the fastest response and read/write performance from SQL as you can. That is important above all else, except having a proper backup strategy completely implemented.

If you are worried about the endurance aspect of an SSD, but not sure you would be happy with the performance of an HDD, then I would suggest you look into the datacenter realm of SSD's. Yes, they are more expensive, but when you are working with critical data, do you really want to run it on a "should be good enough" hardware strategy?

There are a multitude of option available to you, and some at not too crazy of a price. Intel datacenter SSD's are one I would suggest you look into for this. Is it needed? Nope. if you are writing that much on a daily basis, I would absolutely look at a more purpose built component.

I wish you luck!