Dimitri Maziuk wrote (2015/05/20):
> Quoting quantum lto-6 sales blurb
> (http://www.quantum.com/products/tapedrives/ltoultrium/lto-6/index.aspx)
> 
>     Fast backup and restore performance ?at speeds up to 400MB/s (1.4TB/hr)*
> 
> * Assumes 2.5:1 compression for LTO-6, 2:1 for other LTO
> 
> Assuming no compression = 400/2.5 = 160.
> 
> > Seagate NAS drives have a max throughput ranging from 149MB/sec to 
> > 180MB/sec depending on capacity:
> > 
> > http://www.seagate.com/www-content/product-content/nas-fam/nas-hdd/en-us/docs/nas-hdd-ds1789-3-1409gb.pdf
> 
> 160 < 180.
> 
> you get it now?

It should be "min. 160 < max. 180", which is false.

Tape users usually do not want to switch off hardware tape drive
compression and use slower/faster better/worse software compression
instead of it. Also, max. disk speeds are just at the beginning of
the disk. At the end, it is often just 1/3 to 2/3 of the max. speed.
And when the disk is not new, there could be very annoying speed
instabilities due to internal sector reallocations and some other 
mysteries with no-so-bad/good sectors and heads. I have seen small LBA
interval slow downs even up to just 1 MB/s on one 2 TB drive, and the
drive still reported very good SMART values - no reallocations, no
errors.

-- 
Rudolf Cejka <cejkar at fit.vutbr.cz> http://www.fit.vutbr.cz/~cejkar
Brno University of Technology, Faculty of Information Technology
Bozetechova 2, 612 66  Brno, Czech Republic

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