Web-server SSD upgrade: will partial fs switch do?

Question

We had a dedicated server with Hetzner. Once our ecommerce instance got 350+ concurrent users peak we were experiencing some slowdowns and decided to upgrade RAM from 16 to 32GB, as well as adding 240GB SSD drive additionally to our 3TB SATA drive.

It is quite problematic to switch the whole system to SSD, therefore I have a question and hope you will get be understand:

Can I just move /var folder to SSD drive. All our vhost web data is stored in /var/www. Would that increase performance? Or some other essential system elements should be also switched to SSD?

As far as I understand, the benefit of SSD is faster and simultaneous read/write. Will I achieve the benefits by just ensuring faster read/write for our web data?

Looking forward to hearing from you soon.

Thanks for your help

Answer 1

Can I just move /var folder to SSD drive. All our vhost web data is stored in /var/www. Would that increase performance? Or some other essential system elements should be also switched to SSD?

Generally-speaking, most of the OS carries a very low IO load, and can live happily on your non-SSD. You're on the right track suggesting that /var move to the SSD. This will move over your webroot to the faster storage as well as your logs (/var/log). Is /var where your database files reside as well?

As far as I understand, the benefit of SSD is faster and simultaneous read/write.

Let me qualify that - SSDs typically provider higher performance for random IO loads. Most multi-user web services would classify as producing random IO load. For sequential IO loads, spinning disks sometimes will still out-perform SSDs.

To conclude, moving your active IO loads to SSD will likely improve performance. Beyond that, though, the #1 thing you can do to increase performance on this system is to put as much RAM as possible into the system. You should at least have enough RAM to hold your entire database in RAM.

If these steps do not improve performance enough to satisfy your requirements, then you'll need to start looking into moving database to its own system as well as possibly adding a load-balanced cluster of web front ends. That's a completely different topic, though.