Re: petabyte class archival filestore wanted/proposed

[Jeff Anderson-Lee <jonah@eecs.berkeley.edu>]

Bryan Henderson wrote:

>>   1) Tapeless: maintain multiple copies on disk (minimize 
>>backup/restore lag)
>>    
>>
>Can you really call it archival if you're willing to pay 5 times as much 
>for quick access?  Maybe you need a different word.  Archive means large 
>quantities of data with very low access frequency.  And sometimes, in the 
>current legal climate, with very low chance of destruction.
>
>You word this as if the only potential use of tape is backup of disk-based 
>data, but it's also pretty useful as the primary copy of archival data.
>  
>
I know some people swear by them, but our experience with tertiary (tape 
and optical) storge systems has never been positive.  (We have tried 
several over the years, from several vendors.)  Leave it at that, and 
let's just say we want to explore new territory.

There is also an argument that the cost of tape and disk is slowly 
converging/crossing.  Some disagree, we find it an interesting point.

For many users, the cost of archival storage is often dominated by 
non-hardware costs.  Our internal departmental recharge rates for (tape) 
backed-up storage are on the order of $5/month to $10/month per GIGABYTE 
of storage.   That's $60/GB/year to $120/GB/year.  Very little of that 
cost is hardware.   Considering that a GB of disk now costs $1 to $2 for 
commodity disks, I can afford to keep several copies of my data online 
for quick access when I do want it, especially when it is mostly 
archival and doesn't change that often (almost never).

Jeff Anderson-Lee
Petabyte Storage Infrastructure Project
University of California Berkeley