We do publish a calculation that you can use to estimate the "Mean Time to Data Loss" based on the MTBF for each type of drive. You can get the MTBF number from the individual drive manufacturer's web sites.
http://www.netapp.com/tech_library/3027.html#section3.2
In this reference "Data Loss" is defined as "when the failures of two or more disk drives within the same RAID group overlap" This would be the time that you would be required to restore from tape.
As far as actual field numbers... I really don't know ;(
-----Original Message----- From: Brian Tao [mailto:taob@risc.org] Sent: Sunday, July 30, 2000 6:17 PM To: toasters@mathworks.com Subject: Netapp filesystem failure rate
Does Netapp have any numbers that they could share publically on how often they see filesystem failures in the field (i.e., double disk failure, spare drive bug, etc.) that would require restoring all the data from tape? I did a quick count in my head and figured we have roughly 21 filer-years of operation (1 filer running for 3 years, 2 for 2.5 years, etc.) without a catastrophic failure yet. Is the actual observed number more like 50 filer-years? 100? 200?