In article ,
Atro Tossavainen writes:

> Also, the sets the unit presents to hosts cannot consist of disks on
> more than one controller, so sets larger than 7 disks cannot exist
> natively on the controller and one must use the additional software
> RAID facilities of the host OS to combine them into larger partitions.

so what exactly is your point here ? (technically)

No 512 bytes/sector SCSI-LUN can EVER be larger than 2TB.
(AFAIK some Cipricos have the option for 4kbytes/sector => 16 TB LUN,
but the Xserve is 512 bytes/sector only.)
So whatever capacity you buy with the Xserve - above 2TB
you always have to have at least 2 LUNs.

wolfgang

szwolfi@t-online.de (Wolfgang Szoecs) writes:

> so what exactly is your point here ? (technically)
>
> No 512 bytes/sector SCSI-LUN can EVER be larger than 2TB.

You're obviously smarter and better read than I am and thought of
something that didn't even occur to me. Thanks for pointing that out.

--
Atro Tossavainen (Mr.) / The Institute of Biotechnology at
Systems Analyst, Techno-Amish & / the University of Helsinki, Finland,
+358-9-19158939 UNIX Dinosaur / employs me, but my opinions are my own.
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szwolfi@t-online.de (Wolfgang Szoecs) writes:

> In article ,
> Atro Tossavainen writes:
>
> > Also, the sets the unit presents to hosts cannot consist of disks on
> > more than one controller, so sets larger than 7 disks cannot exist
> > natively on the controller and one must use the additional software
> > RAID facilities of the host OS to combine them into larger partitions.
>
> so what exactly is your point here ? (technically)
>
> No 512 bytes/sector SCSI-LUN can EVER be larger than 2TB.

Not with SBC-1, but SBC-2 allows for 64 bit LBAs, or did you mean
something else?

*p

In article , Per Ekman
wrote:

: szwolfi@t-online.de (Wolfgang Szoecs) writes:
:
: > In article ,
: > Atro Tossavainen writes:
: >
: > > Also, the sets the unit presents to hosts cannot consist of disks on
: > > more than one controller, so sets larger than 7 disks cannot exist
: > > natively on the controller and one must use the additional software
: > > RAID facilities of the host OS to combine them into larger partitions.
: >
: > so what exactly is your point here ? (technically)
: >
: > No 512 bytes/sector SCSI-LUN can EVER be larger than 2TB.
:
: Not with SBC-1, but SBC-2 allows for 64 bit LBAs, or did you mean
: something else?

For those who are interested:

http://www.t10.org/ftp/t10/drafts/sbc2/sbc2r14.pdf

See section 5, the READ/WRITE/ETC (16) and (32) commands allow 8 bytes for LBA.

Also, section 4.4 states:

"Logical block addresses are no larger than 8 bytes. Some commands support only
4 byte LOGICAL BLOCK ADDRESS fields (e.g., READ CAPACITY (10), READ (10), and
WRITE (10))."

And, to do the math:

8 bytes * 8-bit bytes = 64-bits

2^64 = 18446744073709551616 blocks
* 512 byte blocks = 9444732965739290427392 bytes

which is roughly 8192 exabytes, or approximately 22 billion 400 gig ATA drives,
or 30 billion 300 gig SCSI drives.

I think we're safe for a few years yet.


Cheers - Tony 'Nicoya' Mantler

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