Re: SGI Altix and Apple Xserve RAID?
From: Tony 'Nicoya' Mantler (nicoya_at_ubb.ca)
Date: 06/14/04
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Date: Mon, 14 Jun 2004 17:39:02 GMT
In article <mjen0365kpp.fsf@curlew.pdc.kth.se>, Per Ekman <pek@pdc.kth.se>
wrote:
: szwolfi@t-online.de (Wolfgang Szoecs) writes:
:
: > In article <pgzvfhyo75n.fsf@kruuna.helsinki.fi>,
: > Atro Tossavainen <Atro.Tossavainen+news@helsinki.finland.invalid> 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 :)
-- Tony 'Nicoya' Mantler -- Master of Code-fu -- nicoya@ubb.ca -- http://nicoya.feline.pp.se/ -- http://www.ubb.ca/ --
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