James G. Sack (jim) wrote:
Andrew Lentvorski wrote:
Gus Wirth wrote:
To add some more information to an excellent summary, in the realm of
Non-Recoverable Error Rates (NRER, a measure of how often the drive
gets it wrong while reading data), enterprise class SCSI drives are at
least an order of magnitude better than most anything else out there.
Back to my previous examples, the Seagate ST3146854LC SCSI drive has a
NRER of 1 in 10^15, while the Western Digital WD1600YS (Enterprise
level server drive ) has a NRER of 1 in 10^14. The WD Raptor line
claims 1 in 10^15.
I've seen those numbers a couple of times, but what do they *mean*?
10^15 bits is approximately 10^14 bytes. That's 100GB.
Ummm, calculate twice, act once?
10^15 bits / 8 bits per byte = 1/8 * 10^15 = .125 * 10^15 = 125 * 10^12
Gahhhh. 10^12 is *Tera*. Stupid. About 100 Terabytes. That's more
reasonable but kinda scary. ZFS with its internal checksums and
recovery is still looking pretty good.
As a side note, when doing rough approximations, taking 1 byte as 10
bits is normally "close enough".
-a
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