[Info-vax] Re; Spiralog, RMS Journaling (was Re: FREESPADRIFT)

[Stephen Hoffman]

On 2016-06-19 01:46:17 +0000, Kerry Main said:

> I am not talking about just OpenVMS . This is platform agnostic and not 
>  specific to any OS. It is also a timeless core principle that is not 
> likely  going to change any time soon.
> 
> 
> As I stated in my previous reply, by its very nature, write back & 
> asynch update strategies increase the risk of a significant event (site 
> lost or  system halted due to HW issue?) causing one to lose data. 
> 
> 
> 
> When you tell an application that the update was completed, and yet no 
> form of data persistence has taken place that transcends at least 2 
> sites, then there is a risk that data will be lost in the event of a 
> site 
> 
> and or server being lost.

And what do you think server-level replication is?  OpenVMS doesn't 
have any concept of this — wait, let me rephrase that, OpenVMS fully 
supports remote server-level replication, you just have to write and 
support and maintain all the necessary code involved — but other 
platforms do have this and are working to add this.   Remote access to 
redundant servers with either fast nonvolatile storage or with a way to 
reliably roll volatile storage to disk during an outage are faster than 
dinking around with tertiary and quaternary storage such as hard disks 
and tape.   Or you use the remote server as a replication log.   Though 
if you're at lower ranges of transactions but have a comparatively 
large budget — where most of the OpenVMS servers I've worked with are 
used — sure, your long-familiar synchronous-write-to SSD or disk works. 
 Even in the lower performance ranges, remote server replication may 
still be of interest, even there.





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