On Mar 7, 2021, at 8:30 PM, Todd Doucet <t...@lambentresearch.com> wrote: > I think one can only get so far with purely qualitative analysis of the > characteristics of SSDs and HDs and then the end of that analysis will be > one-size-fits all advice, for example "recommended" or "not recommended" for > servers.
this +1000 > Surely the answer might vary depending on the particular server usage > pattern, the need for performance, the cost of routine maintenance (swapping > out aging drives or SSDs), the cost of the devices themselves, etc. exactly There's a reason you don't really see 15k enterprise drives anymore. > It seems to me that a given server operator can tell how long a particular > SSD is likely to last. They do not fail randomly, at least not very much. > The fail when they are "used up" and you can figure out well in advance, > usually, when you will need to swap the old ones out of service. Back in 2015 - there's this article https://techreport.com/review/27909/the-ssd-endurance-experiment-theyre-all-dead/ where someone actually bothered to test and report some results. > HDs fail also, obviously, but tend not to be so predictable about it. > Whether it makes sense for a given server to use an SSD really does depend on > the numbers. All drives will fail. All drives will need to be rotated out > of service. It is a matter of cost, convenience, and performance. > > The only caveat I can think of is that there might be an issue of malicious > use--a server with SSDs might be vulnerable to a wear attack, depending on > the server services offered, I suppose. I'm sure there are worst-case scenarios for spinning disks that (in theory) could be exploited to wear their mechanisms out as well. I've personally used both enterprise and consumer SSDs in high-write environments where the cost of replacing the SSDs was worthwhile for the performance benefits (or otherwise didn't change the overall cost of the solution) - and I've been pleasantly surprised with how much more use I've gotten from them than I originally calculated (based on the drive specs + the planed utilization + over provisioning). YMMV of course - but the blanket "you shouldn't use SSDs for servers" or "no one uses SSDs for servers" is wrong. For those who are interested in more details, there are a bunch of good USENIX and ACM papers where people have actually gone and collected data on real-world failure rates. -- Daniel J. Luke
