From the post:

Here’s the math:
(1 – 1 /(2.4 x 10^10)) ^ (2.3 x 10^10) = 0.3835

Change 10^10 to 10^2 and you have roughly the same answer, so it doesn’t seem to matter if you have a high error rate or a low error rate on the drive.

On a 2TB drive (4 * 10^9 sectors) with a 10^15 error rate (the ones Seagate is selling now), the odds of an unrecoverable read error on the first drive is 1/250,000 assuming you have to read every sector to rebuild. The odds of a double-disk failure are miniscule. Even a drive with a 1 in 10^14 error rate means you have only a 1/25,000 odds of a failure.

If your math had been true, we would have lost a LOT of raidsets over the years during rebuilds. We’ve lost some – large (12-14 member) and old RAID5 sets – but not at the rate you seem to be suggesting. With a petabyte of storage on the floor, we frequently go a few weeks without a single drive failing.

I would say that the probability of selling spinning disks 10 years from now is 100% unless there is a significant materials change with NAND. Current silicon based NAND flash can not scale to be price competitive with current hard drives. There is only so small that they can make the cells. They are approaching sizes of only a few atoms thick. And currently each shrink (55nm to 34nm to 25nm) is also reducing the write endurance. Manufacturers have to use extra reserve capacity to counteract the lower write endurance of the newer flash.

"we are still using tape technology and people said that would have been dead ages ago."

Same here. I have a few hundred LTO tapes here at work. I expect to be using tape 10 years from now. NAND certainly will not replace this. Just as hard drives did not either.

@eric… we are still using tape technology and people said that would have been dead ages ago.

An interesting alternative analysis is interface error rate based. Seagate SAS disks list an interface error rate less than one per 10 to the twelfth (10 ^ 12) bits. An undetected error on transfer occurs every 200 thousand sectors over the SATA/SAS interface.

Conclusion: read everything twice to be sure it is correct. Or use RAID-1 and perform checkums on every file read.

First, the probability that ANYONE will still be selling spinning disk storage 10 years from now I would place at <1%. Probably lower than that. SSD will have 300GB, 600G and 900GB drives by the end of the year. As technology improves, more SSD are created and sold, cost will go down, MTBF will continue to climb and URE rates will continue to fall. As you eliminate moving parts, decrease power consumption and heat dissipation, improve the silicon and technology of SSD, which he completely ignores, his entire formula for disk failure starts to change by orders of magnitude. The compute power of storage management subsytems will continue to progress at the same rate as server cpu. His assertion that rebuild times will take longer because of increasing disk size ignores that storage bandwidth could be 100 or 1000X faster than it is today with 10-100X more CPU capacity to tackle the problem.

IMHO, I honestly see this as someone trying to make himself relevant by espousing incomplete theory based on incomplete assumptions regarding the state of technology 10 years from now. Nothing to see here. Move along.

http://www.zetta.net/_wp/?m=200906

ZettaFS is an N+3 configuration.

Others mention in comments that rebuild times are also tremendously important — another factor incorporated in the spreadsheet.