[gpfsug-discuss] SSD LUN setup

[Jonathan Buzzard]

On 17/07/16 03:56, Brian Marshall wrote:
> When setting up SSDs to be used as a fast tier storage pool, are people
> still doing RAID6 LUNs?  I think write endurance is good enough now that
> this is no longer a big concern (maybe a small concern).  I could be wrong.
>
> I have read about other products doing RAID1 with deduplication and
> compression to take less than the 50% capacity hit.
>

There are plenty of ways in which an SSD can fail that does not involve 
problems with write endurance. The idea of using any disks in anything 
other than a test/dev GPFS file system that you simply don't care about 
if it goes belly up, that are not RAID or similarly protected is in my 
view fool hardy in the extreme.

It would be like saying that HDD's can only fail due to surface defects 
on the platers, and then getting stung when the drive motor fails or the 
drive electronics stop working or better yet the drive electrics go puff 
literately in smoke and there is scorch marks on the PCB. Or how about a 
drive firmware issue that causes them to play dead under certain work 
loads, or drive firmware issues that just cause them to die prematurely 
in large numbers.

These are all failure modes I have personally witnessed. My sample size 
for SSD's is still way to small to have seen lots of wacky failure 
modes, but I don't for one second believe that given time I won't see them.

JAB.

-- 
Jonathan A. Buzzard                 Email: jonathan (at) buzzard.me.uk
Fife, United Kingdom.