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