Re: [cobalt-users] Is is possible to "mirror" RAQ2s?

["H.P. Stroebel" <hpstr@xxxxxxxxxxxxx>]

Gerald Waugh schrieb:

> What would one have to do to
> Add a second drive to RaQ2 or RaQ3 and do RAID-1 aka RaQ4?

a second hard drive with raid-1 has nothing to do with a backup. it`s
only sense is to avoid a single hard disk as a single point of failure
(spof).
it protects only against harddisk failures; if a file e.g. is messed up,
these errors are mirrored, too.

mirroring two servers has the same sense, but not to protect against
harddrive failure, but against the whole server as a spof.

under this point of view two raq2/3 hacked to have raid, and a server
mirroring solution like the staqware would not be bad. that is not
high-availability, however, as there are remaining several spofs
(harddrive controllers, nics, routers, power supplies, external power,
switches, hubs etc.)
if you mirror two entire raqs, this would only make sense if they have
at least an independent ups each (there are cute+small 19" solutions by
apc, not very expensive, and should be quite sufficient for a raq) to
avoid power failure as a spof. i would prefer to choose a less expencive
raq, maybe with only 128 mb ram, but a second ups.

backup instead is to protect against data storage failures and user
errors (and to track down intruders) etc; in my opinion, the only
reliable and secure way is an external tape drive; even a dedicated
backup server is a spof, overkill for only one raq, and nevertheless
needs a reliable *external* storage solution.

regular tape backup of a raq that has raid and is mirrored to a standby
server with 2 ups would build a relatively high reliable and inexpensive
combo (for *real* ha solutions one can spend $100.000 without thinking
much about it...)


-- 

H. P.  Stroebel, Germany

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