RE: Disk Size for Nest OS Release of IBM i

If it really is 70GB wouldn't we classify that as "bloatware"? :-)



-----Original Message-----
From: rob@xxxxxxxxx [mailto:rob@xxxxxxxxx]
Sent: Thursday, January 23, 2014 7:22 AM
To: Midrange Systems Technical Discussion
Subject: 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
--
IBM Certified System Administrator - IBM i 6.1 Group Dekko Dept 1600 Mail to: 2505 Dekko Drive
Garrett, IN 46738
Ship to: Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





From: Kirk Goins <kirkgoins@xxxxxxxxx>
To: Midrange-L <midrange-l@xxxxxxxxxxxx>
Date: 01/22/2014 04:36 PM
Subject: Disk Size for Nest OS Release of IBM i
Sent by: midrange-l-bounces@xxxxxxxxxxxx



It has been mentioned here that V7R2 ( or whatever the new release will be
called ) will require a 70GB Loadsource.

The real question here is what size to we really need? I believe this 70GB
drive spec is based in the older SCSI drives not the physical space
required. Where I am going with is vSCSI disks presented to IBM i from
VIOS
or a Hosting IBM i partition or even the size of disks that a SAN will
present to IBM i.

Let's talk 70GB SCSI Drives. If I Mirror my LS with a pair of 70GB drives
then the OS will see 70GB. If my 70GB LS is part of a 4 drive Raid set I
will see only about 53GB. INa 3 drive set I don't know as I Haven't done a
3 drive set but if everything is even that will make those drives around
47GB.


Here's why I ask.
New Power7 with 8 139.5 drives. After Raid5 those drives are 122GB In
this
exampleI want to have an IBM i Hosting partition and 2 IBM i Guests. IBM
suggest to have a minimum of 6 vSCSI drives in a partition for
performance. Now in creating cSCSI drives in IBM i for an IBM i Guest you
loose about 7% if I remember correctly. So each drive on the host needs
to
be about 75GB to present 70GB to the guest. So I need 12 of these. ( 12 x
75 ) = 900GB that will leave about 76GB in the HOST. or about 71% usable
if
you keep the HOST at 90% used. If I can use slightly smaller drives I
would
a little more breathing room or room for a set of OS Image catalogs etc.

No in this example I don't want run any work other than hosting in the
HOST
partition.

Thoughts, Comments etc?

--
Kirk