Re: 8xIntel S3500 SSD in RAID10 on Dell H710p

>
> - disk cache settings (EnDskCache - for SSD should be on or you're going
> to lose 90% of your performance)
>

Disk cache is enabled, I know there is a huge performance impact.

> - OS settings e.g.
>
> echo noop > /sys/block/sda/queue/scheduler
> echo 975 > /sys/block/sda/queue/nr_requests
> blockdev --setra 16384 /dev/sdb
>

I'll try to play with these as well. I haven't tried noop yet, but it was
on my checklist.

> - OS kernel version
>
> We use H710Ps with SSDs as well, and these settings make a measurable
> difference to our performance here (though we measure more than just
> pgbench since it's a poor proxy for our use cases).
>
> Also
>
> - SSDs - is the filesystem aligned and block size chosen correctly (you
> don't want to be forced to read 2 blocks of SSD to get every data block)?
> RAID stripe size? May make a small difference.
>

I read a lot about filesystem alignment, but as far as I understand if I
just format the whole drive and not created any partitions, all should be
aligned. I'll check what is the data block size of SSDs and try set block
size to that, but I'm not exactly sure how does block size work with
RAID10, it seem logical to me that it works differently.

- are the SSDs all sitting on different SATA channels? You don't want them
> to be forced to share one channel's worth of bandwidth. The H710P has 8
> SATA channels I think (?) and you mention 10 devices above.
>

Good question. Since the server is not physical at my place, I will have to
check with the people who assembled it.

Thanks for your help. Once I do more testing, I'll return more details what
helped.