05-25-2010
I just found out that my description of configuring Asynchronous I/O is wrong at all, as in AIX 6.1 there is no aio-pseudodevice any more. Please note that i have deleted the respective part of my earlier post. My apologies for the mistake.
bakunin
---------- Post updated at 01:49 PM ---------- Previous update was at 01:33 PM ----------
Quote:
Originally Posted by
prebila
Thanks for replay.
Lets say that we have 16 disks on storage. And we need one filesystem. Which setup is better regarding performans:
1. We make one raid 10 array and create one lun and present it to aix as one hdiskpower disk ( emc storage ) and make one filesystem on that disk
or
2. We make 4 raid 10 groups ( 4 disks in each ), create one lun on each raid group and present them to aix like 4 hdiskpower disks, and then create one filesystem on that 4 hdiskpowers.
By my opinion second solution is better becouse aix see 4 disks and can paralelly write/read from them.
Regards
Lets take this to the extreme: you could create one LUN and present it to AIX or you could create 16 LUNs (one for each disk) and use AIX to stripe with LVM means over these. In the first case you let the SAN device do the distribution of the I/O load, in the latter the AIX system (namely the LVM) will do this. As it is, a SAN device is a specialized piece of hardware specifically designed to deal with these tasks. I'd bet that the SAN can do that better than AIX, so I'd stick with the SAN machine.
The smallest amount of disk space the LVM deals with is the Physical Partition (PP). If you have a database configured you will probably have one or more multi-gigabyte filesystem and accordingly your disks (and therefore the PP size) will be relatively big - 256MB being a typical value. "Striping" in 256-MB-chunks is probably not all too parallel at all, considering the size of disk clusters and the size of data packets in the SCSI protocoll. In fact your I/O will probably look like this on the device driver level: some (many?) requests to one disk, then some (many?) requests to the next disk, etc.. Not "one request to the first disk, one request to the next disk, ..." at all!
So the answer is: you will be probably better off leaving the I/O-optimization to the SAN device altogether and use the LVM only to logically group filesystems on a per-application (or probably per-Oracle-instance) basis.
I hope this helps.
bakunin
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PARTX(8) System Administration PARTX(8)
NAME
partx - tell the Linux kernel about the presence and numbering of on-disk partitions
SYNOPSIS
partx [-a|-d|-s] [-t TYPE] [-n M:N] [-] disk
partx [-a|-d|-s] [-t TYPE] partition [disk]
DESCRIPTION
Given a device or disk-image, partx tries to parse the partition table and list its contents. It optionally adds or removes partitions.
The disk argument is optional when a partition argument is provided. To force scanning a partition as if it were a whole disk (for example
to list nested subpartitions), use the argument "-". For example:
partx --show - /dev/sda3
This will see sda3 as a whole-disk rather than a partition.
This is not an fdisk program -- adding and removing partitions does not change the disk, it just tells the kernel about the presence and
numbering of on-disk partitions.
OPTIONS
-a, --add
Add the specified partitions, or read the disk and add all partitions.
-b, --bytes
Print the SIZE column in bytes rather than in human-readable format.
-d, --delete
Delete the specified partitions or all partitions.
-g, --noheadings
Do not print a header line.
-l, --list
List the partitions. Note that all numbers are in 512-byte sectors. This output format is DEPRECATED in favour of --show. Don't
use it in newly written scripts.
-o, --output list
Define the output columns to use for --show and --raw output. If no output arrangement is specified, then a default set is used.
Use --help to get list of all supported columns.
-r, --raw
Use the raw output format.
-s, --show
List the partitions. All numbers (except SIZE) are in 512-byte sectors. The output columns can be rearranged with the --output
option.
-t, --type type
Specify the partition table type -- aix, bsd, dos, gpt, mac, minix, sgi, solaris_x86, sun, ultrix or unixware.
-n, --nr M:N
Specify the range of partitions. For backward compatibility also the format <M-N> is supported. The range may contain negative
numbers, for example "--nr :-1" means the last partition, and "--nr -2:-1" means the last two partitions. Supported range specifi-
cations are:
<M> Specifies just one partition (e.g. --nr 3).
<M:> Specifies lower limit only (e.g. --nr 2:).
<:N> Specifies upper limit only (e.g. --nr :4).
<M:N> or <M-N> Specifies lower and upper limits (e.g. --nr 2:4).
EXAMPLES
partx --show /dev/sdb3
partx --show --nr 3 /dev/sdb
partx --show /dev/sdb3 /dev/sdb
All three commands list partition 3 of /dev/sdb.
partx --show - /dev/sdb3
Lists all subpartitions on /dev/sdb3 (the device is used as whole-disk).
partx -o START -g --nr 3 /dev/sdb
Prints the start sector of partition 5 on /dev/sda without header.
partx -o SECTORS,SIZE /dev/sda5 /dev/sda
Lists the length in sectors and human-readable size of partition 5 on /dev/sda.
partx --add --nr 3:5 /dev/sdd
Adds all available partitions from 3 to 5 (inclusive) on /dev/sdd.
partx -d --nr :-1 /dev/sdd
Removes the last partition on /dev/sdd.
SEE ALSO
addpart(8), delpart(8), fdisk(8), parted(8), partprobe(8)
AUTHORS
Davidlohr Bueso <dave@gnu.org>
Karel Zak <kzak@redhat.com>
The original version was written by Andries E. Brouwer <aeb@cwi.nl>.
AVAILABILITY
The partx command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
util-linux February 2011 PARTX(8)