[mdlug] New Server - Hardware Configuration

[Robert Adkins II]

> Robert Adkins II wrote:
> > The plan is to copy all of the data to the hot swap drives and... 
> > 
> > Swap them out every day, every few days.
> 
> 
> Bad idea.  Keep two set of drives permanently installed, set 
> 2 fully mirroring set 1.
> These can (and should) be hot-swappable, but none of these 
> drives should be swapped unless the unit in question fails.
> 

	The plan is to have two sets of drives permanently installed. There
was never any other plan with regards to that. In my research on this, Linux
and the majority of SATA RAID cards out there do not like to mix any RAID
Level and Hot Swap on off the shelf SATA, I have played with that setup
before and discovered with much consternation that it doesn't like to
recognize a new drive added or removed and will potential crap out the
kernel or just corrupt the drive. 

> a THIRD set of hardware addresses should be mapped to 
> hot-swapable bays, and by turning mirroring on and off, a 
> snapshot of the filesystem state can be obtained with no 
> system downtime and only momentary application service downtime.
> 

	While the shop will occassionally run 24 hours a day, the servers
are only required for a typical range of 14 to 18 hours a day. That leaves
me with between 6 to 10 hours to perform a first rsync and then a regular
update of the changes should take considerably less time.

> [I used to work in the financial sector, where this stuff is 
> important -- good backups are required by LAW, and this 
> method works well, both reliably and efficiently.].
> 
> Doing round-robin rotation of your disks is a good way to 
> have all of your disks hit MTBF (mean-time-between-failure) 
> in rapid succession -- which is NOT a good thing.  You want 
> disk failures to be staggered in time, not cascading at you 
> like an avalanche.
> 

	I only plan on performing the round robin rotation on the back-up
discs and if one of those happens to fail, it's really inexpensive to buy
another these days. Really, I'm not concerned about anything beyond a
totally hardware failure of the primary hard drives in the server. All of
the file shares are ran via Samba and I have Samba configured to interpret
any file delete action as a unix mv command with the resulting file being
moved into a "Recycle Bin" which is only accessible to myself as R/W (via
Samba) and RO to a handful of other users. 

	Regards,
	Rob