Re: [Gnumed-devel] Approaches to maintain clinical data uptime

[James Busser]

On Apr 29, 2006, at 4:07 AM, Karsten Hilbert wrote:

> > - primary server... should have 2 hard drives in a hardware RAID 1
> > array,
> I would have one disc for the OS and a RAID 1 mirror (2
> discs) for the data (home dirs and clinical data). Putting
> the OS on another mirror adds comfort (less downtime).

One disc for the OS because... db speed would be improved?

> Such would protect you against *immediately* losing your
> data when one data drive fails... The RAID 1 does not give
> you *zero* downtime - not even concerning failure of a
> single drive.

By "zero downtime" I just meant no "sudden" downtime in the event  
that one drive fails. Maybe I am wrong, but I thought that some  
hardware controllers, despite permitting a RAID 1 array, may not  
continue to read/write on a single drive if the mirror stops  
functioning. And therefore as part of a RAID 1 array choosing, when  
possible, a controller that would continue to run the single drive  
while issuing alerts as one member of the array is failing (or fails).

> The server will have
> to be taken down for replacement of the drive unless you
> have hot-swap hard drives sitting in drive bays.

Mine aren't in drive bays, so a satisfactory scenario would include a  
server array (as above) that could function with one drive failed,  
with a site practice that includes IT support checking of the logs  
for such alerts, and taking down the server at a time chosen to be  
the least disruptive.

> > - what about one's router/firewall which could fail...  would people
> > want to know they can quickly get another of the same model
> LAN switches are pretty much plugin. Outside connectivity
> (eg router) should not be mandatory for a working in-house
> LAN.

Unless the server is located out-of house or is much-accessed from  
outside of house (say from a second surgery location, or else from an  
emergency room where one of the GPs often sees patients who had  
received care in the surgery).

> Firewall replacement should be: boot firewall boot CD in
> another machine with two network cards.

Here are you using dedicated firewall hardware, or a PC, as the  
firewall (or does it matter)? Does "boot CD" mean to upload a config  
file to the firewall which, in order to work, would depend that the  
new firewall is interoperable for that config syntax and settings?

> [re backup contingency] My approach would be:
>
> ... 5) secondary is consistency-checked and promoted to be
>    master DB via Slony

For someone who knew what they were doing ("IT support"), how long  
might the above typically take? Is it the type of procedure that  
could be written down and followed by a GNUmed office administrator  
in the event that the "IT help" is not quickly enough available?

> 7) in the login dialog "GNUmed database on backup" server
>    is selected

What would be the response of the backup server if it would be  
selected by the GNUmed client without it having been promoted to  
master DB via Slony? Would the slave DB refuse to respond?

> > Would people run their media archive off their primary
> primary, should be replicated, too, if downtime is critical

Not clear about the "replication" here. Is it to maintain twin sets  
of media stored in separate physical locations? Would you invest in  
some type of "mirroring" media setup, like 2 cd burners each holding  
a CD for archiving, with a separate cron job backing up to each?