This is not a max disks per vg question. Rather - I have > 2700 disks
on a p595. Anyone know of any limits we might be approaching ? We're
seeing some weirdness. Thanks, Bill.

bjverzal wrote:
>
> This is not a max disks per vg question. Rather - I have > 2700 disks
> on a p595. Anyone know of any limits we might be approaching ? We're
> seeing some weirdness. Thanks, Bill.

Pardon my asking - 2700 disks???

I can understand an unimaginably I/O intense situation using that many "mount
points" to maximize the number of "initiator queues", but my GOD!!!

Do you work for Google or something???!!!

--
David J Dachtera
dba DJE Systems
http://www.djesys.com/

Unofficial OpenVMS Marketing Home Page
http://www.djesys.com/vms/market/

Unofficial Affordable OpenVMS Home Page:
http://www.djesys.com/vms/soho/

Unofficial OpenVMS-IA32 Home Page:
http://www.djesys.com/vms/ia32/

Unofficial OpenVMS Hobbyist Support Page:
http://www.djesys.com/vms/support/

2700 Disks, so thats 3 scalable VGs then .. As long as you know your
LVM limitaitons, then the next issues would be max devices (about
25,000 currently touted with some caveats) or just plain old h/w
resources like memory ..

Ref: p143 of the AIX 5L Differences Guide AIX 5.3 Version

Configuring a large number of devices
The number of devices that AIX can support varies from system to
system,
depending on several important factors. The following factors have an
impact on
the file systems that support the devices:
 Configuring a large number of devices requires storage of more
information in
the ODM device-configuration database. It can also require more device
special files. As a result, more space and more inodes are required of
the file
system.
 Some devices require more space than others in the ODM
device-configuration database. The number of special files or inodes
used
also varies from device to device. As a result, the amount of space
and
inodes required of the file system depends on the types of devices on
the
system.
 Multipath I/O (MPIO) devices require more space than non-MPIO
devices
because information is stored in the ODM for the device itself as well
as for
each path to the device. As a rough guideline, assume that each path
takes
up the space of one-fifth of a device. For example, an MPIO device
with five
paths will have the space equivalent to two non-MPIO devices.
 AIX includes both logical devices and physical devices in the ODM
device-configuration database. Logical devices include volume groups,
logical volumes, network interfaces, and so on. In some cases, the
relationship between logical and physical devices can greatly affect
the total
number of devices supported. For example, if you define a volume group
with
two logical volumes for each physical disk that is attached to a
system, this
will result in four AIX devices for each disk. On the other hand, if
you define a
volume group with six logical volumes for each physical disk, there
will be
eight AIX devices for each disk. Therefore, only half as many disks
could be
attached.
 Changing device attributes from their default settings results in a
larger ODM
device-configuration database and could lead to fewer devices that can
be
supported.
 More devices means more real memory is required.
Two file systems are used by AIX to support devices:
 The RAM file system is used during boot in an environment that has
no
paging space and no disk file systems mounted. The size of the RAM
file
system is 25 percent of the system memory size up to a maximum of 128
MB.
144 AIX 5L Differences Guide Version 5.3 Edition
One inode is allocated for every KB in the RAM file system. If the
system
memory size is 512 MB or larger, then the RAM file system will be at
its
maximum size of 128 MB with 131072 inodes. If either the amount of RAM
file
system space or number of inodes needed to support the attached
devices
exceeds what has been allocated to the RAM disk, the system might not
boot.
If this is the case, you must remove some of the devices.
 The space and inodes of the root file system (rootvg) on the disk
can be
increased as long as there are unallocated partitions in the rootvg.
With the
maximum RAM file system size, it is likely that up to 25,000 AIX
devices could
be configured. These numbers include both physical and logical
devices.
Depending on the various factors mentioned in this section, your
system
might be able to configure more or fewer devices than this number.


HTH
Mark Taylor

bjverzal <bjverzal@gmail.com> wrote:
> This is not a max disks per vg question. Rather - I have > 2700 disks
> on a p595. Anyone know of any limits we might be approaching ? We're
> seeing some weirdness. Thanks, Bill.

Awesome.

How are these disks setup? 20 racks of shelves?

On Jun 21, 12:16 am, Cydrome Leader <prese...@MUNGEpanix.com> wrote:
> bjverzal <bjver...@gmail.com> wrote:
> > This is not a max disks per vg question. Rather - I have > 2700 disks
> > on a p595. Anyone know of any limits we might be approaching ? We're
> > seeing some weirdness. Thanks, Bill.
>
> Awesome.
>
> How are these disks setup? 20 racks of shelves?

In such machine, you should be able to handle at less 4096 disks, but
look for a grand total of 16384 devices (in ODM and in /dev/)