Patrick,
To sum up, neat to see that (from what we can see without having tested
it,) there is (even inexpensive) hardware for this on the market, neat!
My last question related to this would be, what if drives start breaking
down (storage or CacheCade drives), would the OpenBSD system learn to
know somehow, is there any tool or would the MFI driver report it in the
syslog?
(So you as admin will know and can go and shut it down and replace the
broken drive.)
On 2016-02-01 11:14, Patrick Dohman wrote:
Do you know any MegaRaid that a) supports that, b) is modern and not
archaic, and c) is supported by OpenBSD?
It appears the MFI driver provides support for the MegaRAID SAS 9260-8i
Pleas note I’ve not tested the 9260-8i on openbsd
http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man4/mfi.4
<http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man4/mfi.4>
My current understanding is that Cache Cade is licensed add-on for the
9260-8i
that can be configured in the RAID bios.
Without having tried it myself, I share your understanding.
You buy a separate license that is distributed in the form of a tiny PCB
that you mount on the controller card.
http://www.avagotech.com/products/server-storage/raid-controllers/megaraid-ca
checade-pro-software#specifications
<http://www.avagotech.com/products/server-storage/raid-controllers/megaraid-c
achecade-pro-software#specifications>
http://www.avagotech.com/products/server-storage/raid-controllers/megaraid-sa
s-9260-8i
<http://www.avagotech.com/products/server-storage/raid-controllers/megaraid-s
as-9260-8i>
I was mostly considering read acceleration.
Read Ahead caching is supported by the 9260-8i this essentially caches
to
onboard DRAM contiguous blocks if the controllers algorithm determines
they
will be needed.
What I see is that it will use the whole SSD for read acceleration.
BUT, the current version (that is CacheCadePro 2.0) only supports "512GB
of CacheCade [i.e. read acceleration] per controller".
Luckily,
http://docs.avagotech.com/docs-and-downloads/advanced-software/lsi-megaraid-cachecade-software/CacheCadePro2_TechBrief.pdf
points out that an "upcoming release" will support ">2TB".
I emailed them and asked for clarification.
Can you give a practical example of this?
)
A RAID 10 with four disks running enterprise Intel SSD disk drives with
MegaRAID disk caching enabled, Essentially the Intel Enterprise SSD on
board
cache augments the NAND flash. Fault tolerance is provided by a
“capacitor†that flushes the cache to disk after a power loss..
Right - and now we see that actual read acceleration of a magnet HDD
using SSD is possible, that is what CacheCade is about.
