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What is a drive in AIX?

hujirong asked
Medium Priority
Last Modified: 2013-11-17

I am reading these lines from "AIX 5L Practical Performance Tools and Tuning Guide". What does a drive mean in AIX? What I see is all directories. How can I find out what files are on what drive?

"For example, if an application accesses two or more files at the same time, adding an additional disk drive might improve the disk-I/O rate if the files that are accessed at the
same time are placed on different drives."

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A "drive" is typically a physical disk and is represent by "hdisk". If you do an lscfg or even lspv you will see the various hard disks listed. That generally applies to standard SCSi attached, non-raid disks. For physical disks that are part of an array lscfg wont show you each physical disk. The RAID controller usually handles the grouping of physical disks into an array and in turn presents the OS with what it thinks is a physical disk when in reality its multiple disks in a raid array. Using the array tool for you adapter can tell you more about the physical disks in an array.

I would recommend you head over to IBM's redbook site and check out the pSeries system admin study guide, here is link. Pay special attention to chapter 6 where it talks about storage.


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Thank you very much for the detailed reply.

I know we are using SAN. How do I know which one it is? How much can I know about my storage from the following output.:

/home/jihu $ lspv
hdisk0          0007d13d2c7ac2e9                    rootvg          active
hdisk1          0007d13dc0e5928e                    rootvg          active
hdisk2          0007d13dc29e4e04                    ccvg            active
hdisk3          none                                None
hdisk4          none                                None
hdisk5          none                                None
hdisk6          none                                None
hdisk7          none                                None
hdisk8          none                                None
vpath0          0007d13dc0ecc475                    appsvg          active
/home/jihu $ lscfg

The following resources are installed on the machine.
+/- = Added or deleted from Resource List.
*   = Diagnostic support not available.

  Model Architecture: chrp
  Model Implementation: Multiple Processor, PCI bus

+ sys0                                                                System Obj
+ sysplanar0                                                          System Pla
* pci2             U0.1-P1                                            PCI Bus
* pci10            U0.1-P2                                            PCI Bus
* pci11            U0.1-P2                                            PCI Bus
+ ent1             U0.1-P1/E1                                         10/100 Mbp
s Ethernet PCI Adapter II (1410ff01)
* pci12            U0.1-P2                                            PCI Bus
+ fcs1             U0.1-P2-I5/Q1                                      FC Adapter
* fscsi1           U0.1-P2-I5/Q1                                      FC SCSI I/
O Controller Protocol Device
* hdisk7           U0.1-P2-I5/Q1-W10000000C921E333-L5014000000000000  IBM FC 210
* hdisk8           U0.1-P2-I5/Q1-W10000000C92424BC-L5014000000000000  IBM FC 210
* pci1             U0.1-P1                                            PCI Bus
* pci7             U0.1-P2                                            PCI Bus
* pci8             U0.1-P2                                            PCI Bus
+ scsi2            U0.1-P2/Z3                                         Wide/Fast-
20 SCSI I/O Controller
* pci9             U0.1-P2                                            PCI Bus
+ fcs0             U0.1-P2-I3/Q1                                      FC Adapter
* fscsi0           U0.1-P2-I3/Q1                                      FC SCSI I/
O Controller Protocol Device
* hdisk3           U0.1-P2-I3/Q1-W5005076300C215C6-L5014000000000000  IBM FC 210
* hdisk4           U0.1-P2-I3/Q1-W5005076300CA15C6-L5014000000000000  IBM FC 210
* hdisk5           U0.1-P2-I3/Q1-W5005076300C615C6-L5014000000000000  IBM FC 210
* hdisk6           U0.1-P2-I3/Q1-W5005076300CF15C6-L5014000000000000  IBM FC 210
* pci0             U0.1-P1                                            PCI Bus
* isa0             U0.1-P1                                            ISA Bus
+ fda0             U0.1-P1/D1                                         Standard I
/O Diskette Adapter
+ fd0              U0.1-P1-D1                                         Diskette D
* siokma0          U0.1-P1/K1                                         Keyboard/M
ouse Adapter
+ sioka0           U0.1-P1/K1                                         Keyboard A
+ sioma0           U0.1-P1/K1                                         Mouse Adap
+ ppa0             U0.1-P1/R1                                         CHRP IEEE1
284 (ECP) Parallel Port Adapter
+ sa0              U0.1-P1/S1                                         Standard I
/O Serial Port
+ tty0             U0.1-P1/S1-L0                                      Asynchrono
us Terminal
+ sa1              U0.1-P1/S2                                         Standard I
/O Serial Port
+ sa2              U0.1-P1/S3                                         Standard I
/O Serial Port
* ide0             U0.1-P1/Q6                                         ATA/IDE Co
ntroller Device
+ cd0              U0.1-P1/Q6-A0                                      IDE CD-ROM
 Drive I (650 MB)
* pci3             U0.1-P2                                            PCI Bus
* pci4             U0.1-P2                                            PCI Bus
+ ent0             U0.1-P1/E2                                         10/100 Mbp
s Ethernet PCI Adapter II (1410ff01)
* pci5             U0.1-P2                                            PCI Bus
+ scsi0            U0.1-P2/Z1                                         Wide/Ultra
-3 SCSI I/O Controller
+ hdisk0           U0.1-P2/Z1-A8                                      16 Bit LVD
 SCSI Disk Drive (36400 MB)
+ hdisk1           U0.1-P2/Z1-A9                                      16 Bit LVD
 SCSI Disk Drive (36400 MB)
+ hdisk2           U0.1-P2/Z1-Aa                                      16 Bit LVD
 SCSI Disk Drive (36400 MB)
+ ses0             U0.1-P2/Z1-Af                                      SCSI Enclo
sure Services Device
+ scsi1            U0.1-P2/Z2                                         Wide/Ultra
-3 SCSI I/O Controller
* pci6             U0.1-P2                                            PCI Bus
+ L2cache0                                                            L2 Cache
+ mem0                                                                Memory
+ proc1            U0.1-P1-C1                                         Processor
+ proc2            U0.1-P1-C2                                         Processor
/home/jihu $

Typically in a SAN environment the actual arrays will be created/defined on the san itself. You will likely have to access the sans controller and see which physical drives are assigned to what LUN. Chances are the hdisks the aix box sees are allready raid arrays of some type.

The short answer is you can't tell.

You will need to speak to your SAN Admin to find out how the logical disks were created and presented to AIX.  AIX doesn't know if it's using a RAID array or a physical disk and even if it did it wouldn't know what type of RAID array, whether these are exclusive disks or shared with other machines.
Top Expert 2015

No comment has been added to this question in more than 21 days, so it is now classified as abandoned.
I will leave the following recommendation for this question in the Cleanup topic area:

accept Lhotch http:#16383002

Any objections should be posted here in the next 4 days. After that time, the question will be closed.

EE Cleanup Volunteer
Top Expert 2015

Ignoring Graeme_Cowell http:#16659946 as rewording of first answer.
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