[PVE-User] Planning an HA infrastructure : Hardware

Adam Thompson athompso at athompso.net
Mon Feb 3 23:03:14 CET 2014


 

On 2014-02-03 10:23, Philippe Schwarz wrote: 

> 1. A pair of Dell
MD1200 (Disk enclosure with 12 SAS disks in a
> stripped mirror)
connected with SAS cables to each of the blades
> (M620) in a M1000E
enclosure.
> 
> Pros :
> - -Simple
> - - Max IOPS
> - - Each storage is
local for proxmox's point of view (Am i wrong ??)
> 
> Cons:
> -
-Difficult to scale : Up to three blades, it could be easy but after 4
>
ou 5 blades, there won't be enough ports on the SAS disk enclosure.
> 
>
2.The same pair of MD1200 connected to a blade, acting as a ZFS-SAN
>
for the other blades and exporting (NFS or iSCSI) the storage content
>
in an external 10 Gbe connection.
> 
> Pros:
> - - Easy to scale
> - -
Euh...ZFS ;-)
> 
> Cons:
> - - More complicated
> - - Less IOPS due to
the 10Gbe link
> - - More expensive (1 10GBE/blade+1 for the SAN+1 10GBE
switch)

Neither solution will work, since there's no way to physically
connect external SAS disks to an M620 blade. 

The M620 does not have
external SAS ports, and it also lacks a PCIe slot for a SAS HBA. 

The
only M1000 blade that can connect to a SAS enclosure would be an M610x
with an add-in PERC card. This would be an extremely strange
configuration, to say the least, and is not supported. 

Blade servers
are explicitly *not* supported with the PERC H800 cards, as documented
here:
http://www.dell.com/learn/us/en/04/campaigns/dell-raid-controllers?c=us&l=en&s=bsd&cs=04&redirect=1.


However, even if it were possible to connect these components
together, the first solution still will not work. The MD1200 does not
support multi-initiator configurations; the dual (not triple) SAS ports
can only be connected to two SAS ports on the same PERC card, and the
PERC card must explicitly support the MD1200. 

Sorry to burst your
bubble, but you need to go back to square one with this... there's so
much wrong with your solution I can't even suggest how to fix it! 

BTW,
if you already have an M1000e chassis, you should probably be looking at
the Equallogic PS 4110M iSCSI array instead. If you don't already own a
M1000e chassis, purchasing one to hold only three blades is... well...
stupid. You could buy 1U servers (and two MD1200s, and a 10GE switch) to
do the same thing for around 1/4 the price. 

If you really want
blade-like equipement, look at the C6220 instead. That will give you
four servers in a smaller footprint that doesn't require an electrician
to hook up. Add whatever SAS or 10GE or ... cards you want; each node
has a PCIe slot as well as two(?) mezzanine slots. 

-Adam Thompson

athompso at athompso.net 

 
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