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Re: [Linux-cluster] Network-attached power switches for RHCS

On Mon, 2006-10-30 at 10:14 +0800, Mohd Irwan Jamaluddin wrote:
> Good day guys,
> I would like to have your opinion regarding Network-attached power
> switches for Red Hat Cluster Suite (RHCS). I know there are 2 main
> brands available; APC & WTI. Both of them are having several models.
> Below are my finding:
> APC: MasterSwitch plus, 1U, 15A, 120V, (8)5-15 (AP9225)
> http://www.apc.com/resource/include/techspec_index.cfm?
> base_sku=AP9225&ISOCountryCode=us 
> APC: MasterSwitch plus exp, 1U, 15A, 120V, (8)5-15 (AP9225EXP)
> http://www.apc.com/resource/include/techspec_index.cfm?
> base_sku=AP9225EXP# 
> WTI: NetReachâ„¢ Model IPS-800
> http://www.wti.com/specsnr/ips8spex.htm
> WTI: NetReachâ„¢ Model IPS-800-CE
> http://www.wti.com/specsnr/ips8cespex.htm
> >From your experience, which one is better in term or performance,
> reliability & value? If you have any other suggestion, please don't
> hesitate to let me know.

1U APC switches are less expensive and have SNMP capabilities, but to
feed NSPF power to a cluster, you would need at least two of them; the
APC 9225 switches only have one power rail.  This means if you trip over
the switch's power cable, all cluster nodes powered by the APC unit die.
APC switches can also often be daisy chained together, but our agents do
not generally support the configuration.  (I think the CVS version does
on the most recent hardware, but probably not on the 9225...  Jim?)

Ex: single power supplies connected to typical APC devices:

              power1  power2
                |       |
    server A   APC1    APC2   server B
           +----1       1-----+

Ex: dual power supplies connected to typical APC devices:

    server A   APC1           server B
    |      +----1             |      |
    |           2-------------+      |
    |                                |
    |                  APC2          |
    +-------------------1            |

The WTI IPS800 switches above have two power rails with 4 ports each.
The CE version is 208v; the non-CE is 110~120v, otherwise, they're the
same.  They cost more per unit than the 9225.  You can control dual
power supplies on separate rails, giving you NSPF as far as power-cords
are concerned.  If you pull one of the power sources, the power switch
is still accessible and fencing will still work, because the internal
electronics can run off of either power rail.  (I'm not sure what the
fault mode is if the electronics fail, though; I *think* it leaves the
ports in their current states; contact WTI if you have questions about

Ex: dual power supplies connected to typical WTI devices:

    server A   IPS   server B
           +----1    |
               ===   |

Ex: dual power supplies connected to typical WTI devices:

    server A   IPS   server B
    |      +----1    |      |
    |           2----+      |
    |          ===          |
    +-----------5           |

>From a reliability standpoint, APC and WTI both make extremely reliable
devices.  I've never had any switch from either vendor go bonkers on me.

Not to state the opinion of any company I may or may not be employed by
or affiliated with, I personally generally prefer the WTI devices over
APC devices because of:

(a) Design - I *totally* dig the dual power rail configuration.  It has
higher power capacity per switch (30A, 15A per rail/4 ports), as well
two power sources (note: it's *two* rails; not a single, redundant rail,
even though the switch control electronics can run off of either rail)

(b) Firmware revisions on APC devices have broken fencing agents on more
than one occasion. (Though, this isn't so much a problem with the newer
APC SNMP fencing agents, but I don't like setting up SNMP...).

Jim Parsons (current fencing maintainer) has differing opinions on the
matter; I believe he prefers APC units over WTI units.

-- Lon

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