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We have a Rackable Systems server used for backup storage. Recently we purchased a couple 3TB drives to expand the storage, but they are only showing a capacity of 746.52 GB as reported by 3ware's tw_cli utility and the 3ware card's BIOS. I have been searching, but I cannot find a spec sheet that lists the card's maximum single drive capacity supported. I also cannot figure out why the drive shows 746.52 GB instead of 2 TB, if in fact the 2TB compatibility barrier has been reached.

Storage controller: 3ware 9500S-4LP (Firmware: FE9X 2.08.00.009)
Two new drives: Seagate SV35 ST3000VX000 3TB drives.

Are the new drives too large?
Why do the 3TB drives report smaller than the 1TB drive (listed as 931.51 GB)?

Output from tw_cli:

/c1 show

Unit  UnitType  Status         %RCmpl  %V/I/M  Stripe  Size(GB)  Cache  AVrfy
------------------------------------------------------------------------------
u0    SINGLE    OK             -       -       -       372.519   OFF    OFF
u1    SINGLE    OK             -       -       -       931.312   OFF    OFF
u2    RAID-1    OK             -       -       -       745.048   ON     OFF

Port   Status           Unit   Size        Blocks        Serial
---------------------------------------------------------------
p0     OK               u0     372.61 GB   781422768     *snip*
p1     OK               u1     931.51 GB   1953525168    *snip*
p2     OK               u2     746.52 GB   1565565872    *snip*
p3     OK               u2     746.52 GB   1565565872    *snip*

Edit: Added 3ware card firmware version.

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It is quite common for 3TB drives to show up as 750GB on a controller which does not support drives greater than 2.19TiB. (Probably because 3 marketing terabyte minus 2.19TiB is about 750-ish GB). It is not 2TB due to wraparound. –  Hennes Sep 5 '12 at 20:26
    
For what it's worth, my 3ware 9550SX(U)-12 (firmware version FE9X 3.08.00.029) has exactly the same limitation. I tested this with 3TB Hitachi Deskstar 7K3000 HDS723030ALA640 drive. –  user170490 Apr 20 '13 at 20:44
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1 Answer

up vote 4 down vote accepted

As @Hennes said, the 745 GB reported for the 3TB drives is due to the 2.19TB limit imposed by controllers (and apparently this one) that cannot support larger drives. The fault lies in the 32-bit precision offered by LBA32.

Another resource I found here explains the limit is caused by 32-bit LBA. Someone there also reports that 3ware customer service said the 12-port version of this card will not support drives larger than 2TB, so I'm sure mine won't either.

The new 2TB drives we recently ordered are working perfectly, so we'll send the 3TB drives back.

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Be sure to mark your own answer as accepted! This helps the backend to know this question is resolved even if you answered it yourself. –  Aaron Copley Sep 11 '12 at 19:36
    
@AaronCopley Oh, I thought I did. Done. Thanks! –  jimp Sep 11 '12 at 21:21
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