Mark Haney wrote:
On 09/08/2017 09:49 AM, hw wrote:
Mark Haney wrote:
<snip>
It depends, i. e. I can´t tell how these SSDs would behave if large amounts of data would be written and/or read to/from them over extended periods of time because I haven´t tested that. That isn´t the application, anyway.
If your I/O is going to be heavy (and you've not mentioned expected traffic, so we can only go on what little we glean from your posts), then SSDs will likely start having issues sooner than a mechanical drive might. (Though, YMMV.) As I've said, we process 600 million messages a month, on primary SSDs in a VMWare cluster, with mechanical storage for older, archived user mail. Archived, may not be exactly correct, but the context should be clear.
One thing to note, which I'm aware of because I was recently spec'ing out a Dell server: Dell, at least, offers two kinds of SSDs, one for heavy write, I think it was, and one for equal r/w. You might dig into that.
But mdadm does, the impact is severe. I know there are ppl saying otherwise, but I´ve seen the impact myself, and I definitely don´t want it on that particular server because it would likely interfere with other services. I don´t know if the software RAID of btrfs is better in that or not, though, but I´m seeing btrfs on SSDs being fast, and testing with the particular application has shown a speedup of factor 20--30.
Odd, we've never seen anything like that. Of course, we're not handling the kind of mail you are... but serious scientific computing hits storage hard, also.
I never said anything about MD RAID. I trust that about as far as I could throw it. And having had 5 surgeries on my throwing shoulder wouldn't be far.
Why? We have it all over, and have never seen a problem with it. Nor have I, personally, as I have a RAID 1 at home. <snip>
mark