A: Just look at the spec sheets. Look at the mean time between failure (MTBF) ratings for each type of drive. ATA drives are rated lower than those in high-duty cycle environments like RAID arrays.

Drives built for different environments also use different components. The high-end 2.5 million-hour MTBF drives have exotic components such as "fluid dynamic bearing spindle motors," "acoustic and shock dampers" and antiferromagnetically coupled (AFC) media based on glass substrate. Lower cost drives use less exotic components, and have lower ratings for vibration, temperature, shock and acoustics. MTBF ratings range from 300,000 to 500,000 hours, they have lower duty cycles (20% rather than 100%), and variations in power on hours (POH) and start/stop cycles.

--Chris Poelker, storage architect, Hitachi Data Systems

Additional Questions:
	Feb 2004:	The theoretical maximum number of Fibre Channel Arbitrated Loop (FCAL) drives on a loop is 127, but what's a practical number?
	Jan 2004:	What are the variables to consider when determining how many host bus adapters (HBAs) are required per server?
	Dec 2003:	What kinds of tools can help me find files that are no longer used?
	Nov 2003:	Can you please explain what content-addressed storage (CAS) is, and what it's used for?
	Oct 2003:	What do you think of serverless backup?
	Sep 2003:	How do NAS blades in director-class switches work? Will they become popular?
	Aug 2003:	Which is best for consolidating storage in an SAP environment: SAN or NAS?
	Jul 2003:	I have 60% free space on 10,000 PCs. Can I consolidate it by mounting it as a volume and using a login script to map it to the desktops?
	Jun 2003:	Can you describe the steps that a single byte takes when going from memory to a spinning spindle and back again?
	May 2003:	What trends do you see in open-systems backup and recovery environments?
	Apr 2003:	What tools can we use to replicate domestic and overseas databases to one another?
	Mar 2003:	We're building an HSM solution to which we'll write 100GB+/month and store it for seven years. Do you think we should use CD, DVD or tape?
	Feb 2003:	I want to consolidate 10TB+ of files onto one system. Would you recommend products from EMC, NetApp or one based on Microsoft's SAK?
	Jan 2003:	I'm out of disk space on my Sun server running Oracle. Is NAS a good choice?
	Dec 2002:	File server cluster vs. network load balanced vs. DFS: What's the best method for file server HA?
	Nov 2002:	What are the pros and cons of storing user files on a RAID array with either ATA or SCSI drives?
	Oct 2002:	Can you do a LAN-free data transfer by giving an IP address to a FC adapter? Does it decrease the speed of data transfers to LAN speeds?
	Sep 2002:	What is the average amount of hosts for a centralized system to backup at one time?
	Aug 2002:	Why doesn't my mail client software create a lock for e-mail files if it's reading it off a NAS device? Which non-EMC NAS devices provide a gateway to connect to an EMC Symmetrix SAN?
	July 2002:	What does storage pooling mean? What do you think of it?
	May 2002:	What is the difference between a NAS gateway and a SAN appliance? Is tape still the best for archiving media files? Does it offer a lower TCO than disk?
	Apr 2002:	In terms of feed speed, what does that measurement refer to? Is it from the primary storage to the secondary storage? Does it stop at the write speed on the tape drive?
	Mar 2002:	How can you use solid-state disk (SSD) to accelerate SAN performance?