Hi reliability files, writing,reading and maintaining

[Xavier Morel]

Terry Reedy wrote:
> "John Pote" <johnpote at blueyonder.co.uk> wrote in message 
> news:Y15Gf.280109$D47.254492 at fe3.news.blueyonder.co.uk...
>> I would wish to secure this data gathering against crashes of the OS,
> 
> I have read about people running *nix servers a year or more without 
> stopping.
> 
He'd probably want to check the various block-journaling filesystems to 
boot (such as Reiser4 or ZFS). Even though they don't reach DB-level of 
data integrity they've reached an interresting and certainly useful 
level of recovery.

> To transparently write to duplicate disks, lookup RAID (but not level 0 
> which I believe does no duplication).
> 
Indeed, Raid0 stores data across several physical drives (striping), 
Raid1 fully duplicates the data over several physical HDs (mirror raid), 
Raid5 uses parity checks (which puts it between Raid0 and Raid1) and 
requires at least 3 physical drives (Raid0 and Raid1 require 2 or more).

You can also nest Raid arrays, the most common nesting are Raid 01 
(creating Raid1 arrays of Raid0 arrays), Raid 10 (creating Raid0 arrays 
of Raid1 arrays), Raid 50 (Raid0 array of Raid5 arrays), and the "Raids 
for Paranoids", Raid 15 and Raid 51 arrays (creatung a Raid5 array of 
Raid1 arrays, or a Raid1 array of Raid5 arrays, both basically means 
that you're wasting most of your storage space for redundancy 
informations, but that the probability of losing any data is extremely low).