I just installed a new Filer with 72GB BCS drives and they formatted to 68GB. FYI: The only ones that format differently (ZCS vs BCS) are the 36GB disks. Need to be careful here. Ex: A 36GB BCS drive can not “hot Spare” for a 36GB ZCS drive as the BCS drive formats to a lower capacity.

Tom’s math below is accurate, + or – a tad. Nicely done J.

Todd Phillips

Sr. Systems Engineer

Integrated Archive Systems, Inc.

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-----Original Message-----
From: Strange, Steve [mailto:Steve.Strange@netapp.com]
Sent: Saturday, December 15, 2001 11:56 AM
To: 'Tom Yergeau'; Geoff Hardin; toasters@mathworks.com
Subject: RE: Real vs Raw disk space

> 73 GB disks "right sized" to 68000 MB (with zoned checksums.. anyone know if that's the same with block checksums?)

For 73 GB drives, the "right-sized" size is indeed the same for both zone and block checksums.

For 36 GB disks, there's a difference of 1GB between zone and block checksum right-sizings.

Steve

-----Original Message-----
From: Tom Yergeau [mailto:yergeau@speakeasy.org]
Sent: Saturday, December 15, 2001 10:59 AM
To: Geoff Hardin; toasters@mathworks.com
Subject: Re: Real vs Raw disk space

73 GB disks "right sized" to 68000 MB (with zoned checksums.. anyone know if that's the same with block checksums?)

Since you can't use 14 disks and still have a spare, I'm doing this with one seven disk set and one six disk set.

(68000 MB * 7) - 68000 MB (parity) = 408000

(68000 MB * 6) - 68000 MB (parity) = 340000

408000 MB + 340000 MB = 748000 MB

748000 MB * 0.9 = 673200 MB (lose 10% to WAFL)

673200 MB * (1 GB / 1024 MB) = 657.42 GB

So... that would be 657.42 GB usable, assuming no snap reserve.

However, I think if you're buying a DS14 you'll get block checksum disks, which might be right sized to a different size, in which case it would be a different answer. :)

MD

----- Original Message -----

From: "Geoff Hardin" <geoff.hardin@dalsemi.com>

To: "toasters" <toasters@mathworks.com>

Sent: Thursday, December 13, 2001 12:35 PM

Subject: Real vs Raw disk space

Toasters,
   We are looking at purchasing some new DS14 shelves with 72 GB disks.
In order to properly forecast our disk space growth, I was wondering if
anyone out there had taken a look at the difference between real and
usable disk space realized with these new shelves and drives.

  Basically, our environment is as follows:  DS14 Shelf with 14 72 GB
disks (1 RAID group of 8 disks, 1 RAID group of 6 disks), attached to a
filer running DOT 6.1R1P1.  We will have 1 spare disk and no snap
reserve.

Geoff Hardin
geoff.hardin@dalsemi.com