[ale] Tape RAID?

[James Taylor]

I remember working with a Comapq tape RAID about five years ago.  It
used the Compaq RAID controller with a Compaq tape enclosure and 3-5 DLT
drives.  It could be configured as up to 5 separate tape drives or to
appear as a single tape, where the drives were configured in a typical
RAID 5 structure (n-1)/n, one drive space for parity.

As I recall, we ended up breaking the drives into individual backup
devices directl atached to separate servers because the person who
originally spec'ed the solution didn't take physics into account.  It
didn't matter how fast the tape array was if it was faster than tha
network could handle...

-jt
 
 



James Taylor
The East Cobb Group, Inc.
Voice - 770-874-0872
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>>>jkinney at localnetsolutions.com 07/31/04 10:05 am >>> 
Since the write to tape is slow compared to write to HD, is it feasible 
to make a tape RAID process? I have seen several similar things in the 
enterprise realm but they were not quite what I'm envisioning. They 
would do multiple stream backups. All of one file would be on a single 
tape. The next file might be on a different tape. 
 
I'm thinking an evenly split data/parity spread across the array of tape

drives. This would provide all the joys of RAID for a low cost/GB backup

system. The aim is to have a tape system that can accept a data stream 
as fast as the hard drives can deliver it. 
 
This would be a real PIA to do using different tape drives that write at

different speeds. But if the drives all are equivalent, the RAID kernel 
code can be reused to split up the data stream and then a hack on the 
delivery part to support the tape parameters. 
 
Feasible? Bad idea? Been done already? Jim should not try to think 
before the second cup of coffee has been fully ingested? 
-- 
James P. Kinney III          \Changing the mobile computing world/ 
CEO & Director of Engineering \          one Linux user         / 
Local Net Solutions,LLC        \           at a time.          / 
770-493-8244                    \.___________________________./ 
http://www.localnetsolutions.com 
 
GPG ID: 829C6CA7 James P. Kinney III (M.S. Physics) 
<jkinney at localnetsolutions.com> 
Fingerprint = 3C9E 6366 54FC A3FE BA4D 0659 6190 ADC3 829C 6CA7