IS IT POSSIBLE TO SET UP DISK PARTITIONS LARGER
ITEM: RTA000038651
QUESTION:
I understand that the maximum size of a logical volume and a filesystem
in AIX 3.2 is 2GB. I've been told that it is possible to exceed this
limit if the disks are set up as raw devices that are not controlled
by lvm. Is this possible on an RS/6000?
Unitree was mentioned as a possibility.
---------- ---------- ---------- --------- ---------- ----------
A: The maximum size of a logical volume is 2**28 bytes, which is
quite a bit larger than 2 GB. The 2 GB limitation applies only
to jfs filesystems.
As indicated above, you may exceed the 2 GB limit if you use the
logical volume as a raw device. However, the logical volume would
still be controlled by LVM (LVM controls all aspects of logical
volumes, not just special cases such as jfs filesystems).
---------- ---------- ---------- --------- ---------- ----------
QUESTION:
Thanks for the response. 2 to the 28th power is only one-quarter GB.
In thinking about it more, you can set the number of physical
partitions for a logical volume in smit and I just set one to 2048.
Did you mean to say that the limit is 2**28 physical partitions?
Is there IBM documentation that states the limits?
I'm responding to an RFP that requires us to support up to 4GB
partitions.
---------- ---------- ---------- --------- ---------- ----------
A: I apologize for the misinformation. After doing some further
research, I have found that the maximum logical volume can
be about 260 GB in size. This comes from being able to have
up to 1016 PP's per disk (a limit in /usr/include/lvm.h), and
each PP can be as big as 256 MB. This is only possible in 3.2.5,
since support for disks greater than 2 GB in size is allowed.
The only way to achieve such a setup would be by using several RAID
0 drives, where each disk may be comprised of a bank of 5 drives,
each of which can hold 2 GB of data. Each volume group can only
have 32 drives, giving you a maximum limit of 320 GB per volume
group.
However, since AIX 3.2.4 can only support up to 2 GB drives, the
upper limit on a volume group decreases to 64 GB (2 GB per disk *
32 disks per VG). Thus, the upper limit on a raw logical volume
will also be 64 GB in AIX 3.2.4.
The 64 GB limit for AIX 3.2.4 is available in the "1993 /AIXtra
Technical Conference". My sources for the 3.2.5 limit came from
the lvm.h header file referenced above, and InfoExplorer (for the
256 MB/PP limit, documented with the "mkvg" command).
---------- ---------- ---------- --------- ---------- ----------
QUESTION:
I need a little more clarification. The system will be 3.2.5 only.
1) Can you set up a 4GB raw partition using RAID 1, 3 or 5 on a 7135?
2) Can you set up a 4GB raw partition (mirrored, so 8GB total) using:
- available IBM 9334 or internal RS/6000 SCSI disks?
- available IBM 9333 disks?
---------- ---------- ---------- --------- ---------- ----------
A: Yes, you can set up the 4 GB raw LV using both scenarios that you
proposed. The disks used are irrelevant -- the only thing that
matters is that the disk space is there. I mentioned using RAID
only because that is the only way to reach the theoretical 260 GB
limit for a LV. Since your requirements are somewhat smaller,
9333, 9334, or SCSI disks will be quite sufficient.
---------- ---------- ---------- --------- ---------- ----------
This item was created from library item Q652366 CPLQW
Additional search words:
CNTL CONTROL CONTROLLER CPLQW CTL CTRL DASD DISC DISKETTE IX LARGER
LVM MANAGEMENT MAR94 OP OUTSIDE OZNEW PARTITIONS POSSIBLE RISCMGMT
RISCSYSTEM SET SETTING SOFTWARE SYS SYSTEM UP 2GB
WWQA: ITEM: RTA000038651 ITEM: RTA000038651
Dated: 03/1996 Category: RISCMGMT
This HTML file was generated 99/06/24~12:43:15
Comments or suggestions?
Contact us