🚀 go-pugleaf

Tom Kustner (emjay@execpc.com) wrote:
> 
> : I have done some research on this and drawn some conclusions
> : (corrections welcome), but still have a few questions:
> :
> : Duplexing
> :
> : - Initially cheaper than RAID 5, but eventually more expensive (twice
> :   the drives)
> 
> While I haven't performed a cost-analysis vis-a-vis the number of drives
> in the array vs. the duplexing, my understanding is that with the RAID,
> your cost will be dependent on the number of drives that you have on the
> array; ie. 3 drives?  5 drives?
> 
> : We are a Compaq environment and currently duplexing our current
> : server.  These questions are more for a new server we may be ordering
> : from Compaq (Proliant 1500).  Any comments on Compaq's RAID  solutions
> : or on their SmartArray controllers are welcome.  Thanks for your help.
> 
> One of the sites where I'm involved in is a Compaq shop, and they have
> about 10 servers; with the exception of a ProLiant 2000 with the Compaq
> Smart ARRAY controller, the rest are Compaq ProSignias with the the
> integrated CPQ SCSI adapter and an Adaptec EISA adapter (duplexed).  The
> ProLiant 2000 has grown to a 4 2.1 GB RAID 5 array with 64 MB of RAM and I
> have all the confidence in Compaq's SmartARRAY controllers.  They seem to
> be well designed, engineered (battery-backup too!), and if implemented
> properly (keep an eye out on the software updates and driverss), they
> should be a suitable fault-tolerant platform.
> 
> By the way, the RAB (RAID Advisory Board) publishes some white papers and
> or documents about the pros and cons and the virtues of RAID, etc.  Let me
> know if you need a copy or can't find one.  I may have some lying around
> literature center.
> 
> Regards,
> 
> --
>  David Tay                              | E-mail    : tsr@clark.net
>  Tay Systems Research                   | CompuServe: 74213,2471
>  3554 Chain Bridge Road, Suite 100      | Telephone : +1-703-760-9022
>  Fairfax, VA 22030-2709, U.S.A.         | Facsimile : +1-703-893-1154

FWIW, I have a Proliant 2000 with 5 2Gig drives, 4 of which are RAID 5 
giving me a net 6 Gig of space, and the fifth drive as a hot swappable 
drive.  The machine has been ultra reliable, although my philosopy is to 
focus not on the mean time between failures but on the mean time of the 
failure.

RAID 5 is obviously more cost effective given that duplexing gives only 
half the gross disk storage whereas RAID 5 gives (n-1)/n times the gross 
space (n = number of drives).

'Cost' penalty with RAID is that to add extra drive capacity, volumes 
will need to be re-created.  OTOH, I've had it put to me that duplexing 
has inherent risks because if there is a corruption, the corruption can 
be duplexed, giving no protection.