Re: Disk Size for Nest OS Release of IBM i

In all the times that I've seen a jump from one load source size to
another I've never seen anyone give any concern to size lost to raid
striping. Since the previous size was only 35gb and the new one is 70gb I
would like to think that it doesn't need all 70gb, but that 35gb sure
wasn't cutting the mustard any more. I would bet that 70GB is overkill
but IBM just went with the next available size increase. And, that they
don't like to dance on the edge of a knife so they won't tell you exactly
what is needed.

You are probably wrong in your calculations about the 3 drive SCSI raid
set. It's worse. In scsi drives the raid striping occurs across 2, 4 or
8 drives; depending on how many drives were in the raid set when it was
first included. So in a scsi 3 drive raid set you'll end up with 35, 35
and 70, because the first two drives will have the raid striping. NEVER
use a three drive raid set in a scsi setup. The performance will also
take a hit because the striping is only on two drives. On a four drive
set you'll end up with 52.5, 52.5, 52.5, 52.5 and balanced striping. SAS
drives are different. On a three drive set the striping should be spread
across all three drives. Don't take my word - verify.
The 3 drive raid set performance issue on scsi drives is not specific to
IBM i. Other platforms all tell you to shy away from it.

HOST:
WRKNWSSTG
%
Name Used Size

MAIL1D101 0 140003
MAIL1D102 0 140003
MAIL1001 0 140003
MAIL1002 0 140003
MAIL1003 0 140003
MAIL1004 0 140003
MAIL1005 0 140003
MAIL1006 0 140003
MAIL1007 0 140003
MAIL1008 0 140003
MAIL1009 0 140003
MAIL1010 0 140003
MAIL1011 0 140003
MAIL1012 0 140003
MAIL1013 0 140003
MAIL1014 0 140003
MAIL1015 0 140003
MAIL1016 0 140003
WRKLNK '/QFPNWSSTG/*'
Object link Typ
. DIR
.. DIR
MAIL1D101 DIR
MAIL1D102 DIR
MAIL1001 DIR
MAIL1002 DIR
MAIL1003 DIR
MAIL1004 DIR
MAIL1005 DIR
...
WRKLNK '/QFPNWSSTG/MAIL1D101/*'
Object link Type
. DIR
.. DIR
QFPCLTSTG1 STMF
QFPCONTROL STMF
QFPSIDEFIL STMF

QFPCLTSTG1
Size of object data in bytes . . . . . : 146804801536
Allocated size of object . . . . . . . : 146841534464
QFPCONTROL STMF
Size of object data in bytes . . . . . : 512
Allocated size of object . . . . . . . : 8192
QFPSIDEFIL STMF
Size of object data in bytes . . . . . : 1024
Allocated size of object . . . . . . . : 8192

GUEST:
WRKDSKSTS
Size
Unit Type (M)
1 6B22 130493
2 6B22 130493
3 6B22 130493
4 6B22 130493
5 6B22 130493
6 6B22 130493
7 6B22 130493
8 6B22 130493
9 6B22 130493
10 6B22 130493
11 6B22 130493
12 6B22 130493
13 6B22 130493
14 6B22 130493
15 6B22 130493
16 6B22 130493
17 6B22 130493
18 6B22 130493


Rob Berendt