How to enable powerpath failed path in a faster way

By unplug one of the Fiber cable to simulate FC HBA failure, the result as expect:

[root@VMXDB01 ~]# powermt display
Symmetrix logical device count=39
CLARiiON logical device count=0
Hitachi logical device count=0
Invista logical device count=0
HP xp logical device count=0
Ess logical device count=0
HP HSx logical device count=0
==============================================================================
----- Host Bus Adapters ---------  ------ I/O Paths -----  ------ Stats ------
###  HW Path                       Summary   Total   Dead  IO/Sec Q-IOs Errors
==============================================================================
   3 qla2xxx                       optimal      39      0       -     0      0
   4 qla2xxx                       failed       39     39       -     0     39


[root@VMXDB01~]# powermt display dev=emcpowera
Pseudo name=emcpowera
Symmetrix ID=0009899012321
Logical device ID=0141
state=alive; policy=SymmOpt; priority=0; queued-IOs=0
==============================================================================
---------------- Host ---------------   - Stor -   -- I/O Path -  -- Stats ---
###  HW Path                I/O Paths    Interf.   Mode    State  Q-IOs Errors
==============================================================================
   3 qla2xxx                   sdbe      FA  7aA   active  alive      0      0
   4 qla2xxx                   sdce      FA  9aA   active  dead       0      1

After put back the fiber cable, it takes 5 minutes to detect this recovery action and change the state to "alive".

How to make it faster? the answer is to use "powermt enable hba=#hba" to enable the hba (path) manually. Here #hba is referring to the first column of the output (hba is 3 or 4)

[root@VMXDB01 ~]# powermt enable hba=4

Symmetrix parition alignment (Windows and Linux)

On Linux/Winows, first 63 blocks has been reserved for MBR (master boot record), and first data partition starts with offset at 63*512bytes=31.5KB.

However, Symmetrix array define tracks to be 64KB on DMX-3 and later (32KB for DMX-2 and earlier). This misalignment can use misalignment on Symmetrix memory cache (Just imaging one 64KB track on Host mapping to 2 tracks in the memory cache and storage), this will cause performance degradation.

Below steps shows how to manually perform the alignment using fdisk:
(128 blocks x 512bytes/block = 64KB)

[root@VMXDB01 ~]# fdisk /dev/emcpowera
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklab
Building a new DOS disklabel. Changes will remain in memory only,
until you decide to write them. After that, of course, the previous
content won't be recoverable.

Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

Command (m for help): n             <-- New partition
Command action
   e   extended
   p   primary partition (1-4)
p                                   <-- Primary partition
Partition number (1-4): 1           <-- 1st partition
First cylinder (1-1011, default 1): <-- leave default to use 1st cylinder
Using default value 1 
Last cylinder or +size or +sizeM or +sizeK (1-1011, default 1011):  <-- Default
Using default value 1011

Command (m for help): x             <-- enter eXpert mode

Expert command (m for help): p      <-- print partition table

Disk /dev/emcpowera: 67 heads, 62 sectors, 1011 cylinders

Nr AF  Hd Sec  Cyl  Hd Sec  Cyl     Start      Size ID
 1 00   1   1    0  66  62 1010         62    4199632 83
 2 00   0   0    0   0   0    0          0          0 00
 3 00   0   0    0   0   0    0          0          0 00
 4 00   0   0    0   0   0    0          0          0 00

Expert command (m for help): b      <-- move to beginning of the partition
Partition number (1-4): 1           <-- choose 1st partition
New beginning of data (62-4199693, default 62): 128     <-- Enter starting block

Expert command (m for help): p      <-- print partition table

Disk /dev/emcpowera: 67 heads, 62 sectors, 1011 cylinders

Nr AF  Hd Sec  Cyl  Hd Sec  Cyl     Start      Size ID
 1 00   1   1    0  66  62 1010        128    4199566 83
Partition 1 has different physical/logical beginnings (non-Linux?):
     phys=(0, 1, 1) logical=(0, 2, 5)
 2 00   0   0    0   0   0    0          0          0 00
 3 00   0   0    0   0   0    0          0          0 00
 4 00   0   0    0   0   0    0          0          0 00

Expert command (m for help): w      <-- save partition table
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[root@VMXDB01 ~]# fdisk -l /dev/emcpowera

Disk /dev/emcpowera: 2150 MB, 2150891520 bytes
67 heads, 62 sectors/track, 1011 cylinders
Units = cylinders of 4154 * 512 = 2126848 bytes

         Device Boot      Start         End      Blocks   Id  System
/dev/emcpowera1               1        1011     2099783   83  Linux
Partition 1 has different physical/logical beginnings (non-Linux?):
     phys=(0, 1, 1) logical=(0, 2, 5)

Exploring EMC Storage: Introducing Symmetrix Software

EMC Solutions Enabler Kit

Contains all the base management software that provides a host with SYMAPI-shared libraries and the basic Symmetrix command line interface (SYMCLI)

What is SRDF?

The Symmetrix Remote Data Facility (SRDF) is a business continuity solution to replicate between Symmetrix storage arrays.

SRDF currently supports the followin modes of operation:

1. Synchronous mode (SRDF/S)
2. Asynchronous mode (SRDF/A)
3. Adaptive copy mode (transferring data regardless of order/consistency)

What is EMC TimeFinder?

TimeFinder is replicating data within a Symmetrix storage array.

• TimeFinder/Mirror - Genral monitor and control operations for Business continuance Volumes (BCV)
• TimeFinder/CG - Consistency groups
• TimeFinder/Clone - Clone copy
• TimeFinder/Snap - Snap copy

What is PowerPath?

PowerPath is host-based software that works with networked storage systems to intelligently manage I/O paths. PowerPath manages multiple paths to a storage array. Supporting multiple paths enables recovery from path failure because PowerPath automatically detects path failures and redirects I/O to other available paths.

A key feature of path management in PowerPath is dynamic, multipath load balancing.

What is EMC Replication Manager?

Replication Manager has a generic storage technology interface that allows it to connect and invoke replication methodologies available on:

• EMC Symmetrix arrays
• EMC CLARiiON arrays
• HP StorageWorks arrays

Exploring EMC Storage: Introducing Clariion Storage

Clariion array was originally designed for AViiON computer within Data General Corporation, and acquired by EMC on 1999. Occupying the entry-level and mid-range of EMC's SAN disk array product palette, it is complemented by the high-end Symmetrix.

CLARiiON AX-Series

• AX4: level disk array, support upto 60 SAS/SATA disks through expension pack, with total capacity 60TB

CLARiiON CX-Series

• CX-300/CX-300i/CX-500/CX-500i/CX-700: End-of-Life Product, each with unique data-in-place upgrade to the next level. ("i" inside the product name refers to "iscsi")


• CX3 Model 10/CX3 Model 20/CX3 Model 40/CX3 Model 80: each with unique data-in-place upgrade to the next level.

• CX4 Model 120/CX4 Model 240/CX4 Model 480/CX4 Model 960: each with unique data-in-place upgrade to the next level. Number (120/240/480/960) in the product represents maximum disk drives, and maximum capacity.

Reference:

http://en.wikipedia.org/wiki/Clariion

http://www.dg.com/collateral/hardware/comparison/emc-clariion.htm

Exploring EMC Storage: Introducing Symmetrix Storage

Symmetrix storage is designed for high-end, contrasting to Clariion, which is targeting to entry-midsize market.

These EMC Symmetrix product before DMX-2 have been omitted.

DMX-2 configurations: (Based on Direct Matrix Architecture)

• Symmetrix DMX-800EL: 8-60 drives, 4-64 GB cache memory, 8 x 2 GB FC front ends, modular rack mount
  
• Symmetrix DMX-800: 60-120 drives, 4-64 GB cache memory, 16 x 2 GB FC front ends, modular rack mount
  
• Symmetrix DMX-1000: up to 144 drives, 64-128 GB cache memory, 48 x 2 GB FC front ends, single cabinet
  
• Symmetrix DMX-2000: up to 288 drives, 128-256 GB cache memory, 64 x 2 GB FC front ends, two cabinets
  
• Symmetrix DMX-3000: up to 576 drives, 128-256 GB cache memory, 64 x 2 GB FC front ends, three cabinets

DMX-3 configurations:

• Symmetrix DMX-3 950: non-expandable version of Symmetrix, up to 360 drives, up to 128 GB cache memory, 8 front-end ports, one or two cabinets
  
• Symmetrix DMX-3: up to 2400 drives, up to 512 GB cache memory, 64 x 2 GB FC front ends (even 4 Gb FC's are available at this time), two to nine cabinets

DMX-4 configurations:

• Symmetrix DMX-4: up to 1920 drives (or up to 2400 drives for 500 GB drive only configurations), up to 512 GB cache memory, 64 x 4 GB FC front ends, two to nine cabinets

V-Max configurations: (Based on Virtial Matrix Architecture)

• Symmetrix V-Max SE: a entry point single enginee storage system
• Symmetrix V-Max: high-end storage array that scales from a single configuration with a dedicated system cabinet and a single storage bay to a larger eight-engine configuration with up to 10 storage bays capable of holding 2400 physical disk drivers.

Reference:

http://en.wikipedia.org/wiki/EMC_Symmetrix

EMC Symmetrix DMX Architecture Product Description Guide

Oracle Databases on EMC Symmetrix Storage Systems