DMX-4 Interview Questions
VCM Database
The Symmetrix Volume
Configuration Management
(VCM)
database stores
access configurations
that are used
to grant host
access
to logical
devices in a Symmetrix storage array.
The VCM
database resides on a
special system
resource logical device,
referred to as the
VCMDB
device, on each Symmetrix storage array.
Information stored in the VCM database includes, but
is not limited to:
· Host and
storage World Wide Names
· SID Lock
and Volume Visibility settings
· Native logical device data,
such as the front-end
directors
and storage ports to
which they are mapped
Masking operations
performed on Symmetrix storage devices
result in
modifications to the VCM database in
the
Symmetrix array. The VCM database can be backed
up, restored, initialized
and activated. The Symmetrix SDM
Agent must
be running in order to perform VCM
database operations
(except deleting backup
files).
Regarding the VCMDB, now this DB resides on the the
two SFS (Symmetrix File System) volumes that are automatically created
when
binfile is build. You can identify them easily on
bin. A small volume called still
called VCM must
still be created
but it will be used just as a normal
gatekeeper
DMX-4 Storage Provisioning
Step by Step
Step by Step Procedure for storage provisioning
& Reclamation
in DMX-4
Storage Provisioning
· Creating STD device
· Forming Meta Device
· Mapping
· Masking
Storage Reclamation
· Unmasking
· Write Disable
· Un-mapping
· Dissolve meta
· Deleting hypers
Step by Step Procedure for storage provision in DMX-4
· Creating STD
device
· Verify the Symmetrix status
symconfigure –sid
4282 verify
· If
any hung
activities found
abort
symconfigure
–sid 4282 abort
· Verify the available free space
symconfigure
-sid SymmID [-v
| -freespace [-units
cylinders | MB]] list
or
symdisk –sid 4282
list
–disk_group 2
· Create Command file
Create dev count=8, size=12394, data_member_count=3,
emulation=FBA, config=RAID-5,
disk_group=2;
· Verify the command line syntax by performing PREVIEW using Symconfigure command
Symconfigure –sid
4282 –f Create_hypers.txt –v
–noprompt preview
· Verify the Array readiness
by performing PREPARE using Symconfigure command
Symconfigure –sid
4282 –f Create_hypers.txt –v
–noprompt prepare
· Execute COMMIT using Symconfigure command
Symconfigure –sid
4282 –f Create_hypers.txt –v
–noprompt commit
· Verify the newly created
devices
Symdev –sid
4282 list –noport
· Forming
Meta Device
o Verify the
Symmetrix status
symconfigure
–sid 4282 verify
o If any hung activities
found abort
symconfigure
–sid 4282 abort
o Create Command file
Form meta from dev 26CA, config=striped, stripe_size=1920;
add dev 26CB:26E4 to meta 26ca;
o Verify the command
line
syntax by performing PREVIEW using Symconfigure
ommand
Symconfigure –sid
4282 –f meta.txt –v –noprompt preview
o Verify the
Array readiness
by performing PREPARE
using Symconfigure
command
Symconfigure –sid
4282 –f meta.txt –v –noprompt prepare
o Execute COMMIT using Symconfigure
command
Symconfigure –sid
4282 –f meta.txt –v –noprompt commit
o Verify the
newly created meta devices
Symdev –sid
4282 list –noport
· Mappping
· Find
the
host connected
Director and Port details
symcfg –sid 4282 list
–connections
o Find the available addresses on that
port
symcfg –sid 4282 list
–address –available
–dir 7d –p 0
o Create a command file for mapping
map dev
26ca to dir 7d:0, lun=036;
o Verify the command
line
syntax by performing PREVIEW using
Symconfigure command
symconfigure
–sid 4282 –f create_hypers.txt
–v –nop preview
o Verify the
Array readiness
by performing PREPARE
using
Symconfigure command
symconfigure
–sid 4282 –f create_hypers.txt
–v –nop prepare
o Execute
COMMIT
using Symconfigure
command
symconfigure
–sid 4282 –f create_hypers.txt
–v –nop commit
o Check the device have been
mapped
symcfg –sid 4282 list
–address –available
–dir 7d –p 0
· Mappping
o Masking devices to the host
symmaskdb –sid 4282
–wwn 10000000c93f62cf
–dir 7d –p 0 add devs 26ca –nop
Symmask –sid 4282 –refresh
o Check whether
devices have masked
symmaskdb -sid 4282 list
database -dir 7d -p 0
Step by
Step Procedure for Storage Reclamation
· Unmasking
o Unmasking devices
from the host
symmaskdb –sid 4282
–www 10000000c93f62cf –dir
7d –p 0 remove devs
26ca
o Refresh
the Symmetrix Array
Symmask –sid 4282 –refresh
· Write Disable
o Write Disable the devices
before unmapping from the
Director and
from port
symdev -sid 4282
write_disable 26ca -sa
7d -p 0 -noprompt
· Un-mapping
o Create a cmd/txt file
with the following line
Unmap dev 26ca
from dir all:all;
o Perform
preview operation using
symconfigure command
Symconfigure –sid 4282 –f unmap.txt –v –nop preview
o Perform
prepare operation using
symconfigure command
Symconfigure –sid
4282 –f unmap.txt
–v –nop prepare
o Perform
Commit operation
using symconfigure command
Symconfigure –sid
4282 –f unmap.txt
–v –nop commit
o Verify that
the device has been
unmapped
Symdev –sid
4282 list –noport
· Dissolve meta
o To Dissolve meta
create a cmd/txt file
with the following line
Dissolve meta dev
26ca;
o Perform
preview operation using
symconfigure command
Symconfigure –sid 4282 –f dissolve.txt –v –nop preview
o Perform
prepare operation using
symconfigure command
Symconfigure –sid
4282 –f dissolve.txt
–v –nop prepare
o Perform
Commit operation
using symconfigure command
Symconfigure –sid
4282 –f dissolve.txt
–v –nop commit
o Verify that
the meta has been Dissoved.
Symdev –sid
4282 list –noport
· Deleting hypers
o To delete the hypers
create
a cmd/txt file with the following line.
Delete dev 26ca:26d1;
o Perform
preview operation using
symconfigure command
Symconfigure –sid 4282 –f dissolve.txt –v –nop preview
o Perform
prepare operation using
symconfigure command
Symconfigure –sid
4282 –f dissolve.txt
–v –nop prepare
o Perform
Commit operation
using symconfigure command
Symconfigure –sid
4282 –f dissolve.txt
–v –nop commit
o Verify that
Hypers
have been
deleted.
Symdev –sid
4282 list -noport
SymCli 7 Commands
brief description
Symmetrix Command
Line Interface Commands
Brief Description
SYMCLI BASE
Commands
symapierr - Used
to translate SYMAPI error code numbers into
SYMAPI error messages.
symaudit - List records from
a Symmetrix audit log file.
symbcv - Perform BCV
support operations
on Symmetrix BCV
devices.
Symcfg
- Discover or display Symmetrix configuration
information.
symchg - Monitor changes
to Symmetrix devices
or to logical objects stored on
Symmetrix devices.
symcli -
Provides the version number and a brief description of the commands included in
the Symmetrix Command Line
symdev - Perform
operations on a device given the device's
Symmetrix name. Can also be used to view Symmetrix device
locks.
symdg - Perform
operations on a device group (dg).
symdisk - Display
information about the disks within a Symmetrix.
symdrv - List
DRV devices on a Symmetrix.
symevent - Monitor
or inspect the history of events within a Symmetrix.
symgate - Perform
operations on a gatekeeper device.
symhost - Display
host configuration information and performance stats syminq - Issues a SCSI Inquiry command on one
or all device interface symipsec -
Administers IPSec encryption on Gigabit Ethernet connections symlabel - Perform label support operations on a
Symmetrix device.
symld - Perform
operations on a device in a device group (dg).
symlmf -
Registers SYMAPI license keys.
sympd - Perform
operations on a device given the device's physical name.
symsg - Perform
operations on a storage device group (sg).
symstat - Display
statistics information about a Symmetrix, a Director, a device group, or a
device.
symreturn - Used
for supplying return codes in pre-action and post-action script files.
symaccess -
Administer Symmetrix Access Logix.
symacl -
Administer Symmetrix access control information. symauth - Administer Symmetrix user authorization
information. symcg - Perform
operations on an composite group (cg).
symchksum -
Administer checksum checks when an Oracle database writes data files on
Symmetrix devices.
symclone - Perform
Clone control operations on a device group or on a device within the device
group.
symconfigure - Perform modifications on the Symmetrix
configuration.
symconnect - Setup
or Modify Symmetrix Connection Security functionality.
symfast -
Administer Symmetrix FAST (Fully Automated Storage Tiering) policies,
associations, and the FAST Controller.
symmaskdb - Backup,
Restore, Initialize or Show the contents of the device masking database.
symmigrate -
Migrates the physical disk space associated with a Symmetrix device to a
different data protection scheme, or to disks with different performance
characteristics.
symmir - Perform
BCV control operations on a device group or on a device within the device
group.
symoptmz - Perform
Symmetrix Optimizer control operations.
symqos - Perform
Quality of Service operations on Symmetrix Devices.
symrcopy - Perform
Symmetrix Rcopy control operations on devices in a device file.
symrdf - Perform
RDF control operations on a device group or on a device within the device
group.
symrecover - Perform
automated SRDF session recovery operations.
symsan - List
ports and LUNs visible on the SAN
symsnap - Perform
Symmetrix Snap control operations on a device group or on devices in a device
file.
symstar - Perform
SRDF STAR management operations. symtier
- Create and manage storage tiers within a Symmetrix. SYMCLI
SRM(Mapping) Commands
symhostfs - Display
information about a host File, Directory, or host File System.
symioctl - Send IO
control commands to a specified application.
symlv - Display
information about a volume in Logical Volume Group (vg).
sympart - Display
partition information about a host device.
symrslv - Display
detailed Logical to Physical mapping information about a logical object stored
on Symmetrix devices.
symvg - Display
information about a Logical Volume Group (vg).
create a zone and place it in the vsan #
zone
name testzone1 vsan
4
add a member (port wwn example) # member pwwn
10:00:00:00:c9:21:40:b8 (port
on the host) add a member (fabric port wwn example)
# member fwwn 10:01:10:01:10:ab:cd:ef
(port
on the switch)
add a member (FCID example - hard
zoning) # member fcid 0x7f0000 (24 bit address)
add a member (FC
alias example) # member fcalias payroll
MDS-series
common commands
display logged in WWN, display vsan information # show flogi database display the specific vsan logins # show fcns database vsan 4
activatng a zoneset
# zoneset activate
name
zone1 vsan 4
delete a zoneset # clear zone dataabse vsan 4
configure the default zone #
zone
default-zone permit vsan 4 display zones
and zonsets # show zoneset
active
# show zoneset
# show zoneset active vsan
4
copy active zone set to the full zone set # zone copy active-zoneset
full-zoneset
vsan 4 distribute the full zoning database to others switches
# zoneset distribute full vsan 4
=====================================================================
===================================
Creating zone by WWN zonecreate "zone1", "20:00:00:e0:69:40:07:08 ;
50:06:04:82:b8:90:c1:8d"
Create
a zone configuration
cfgcreate "test_cfg", "zone1 ; zone2"
saving the zone configuration cfgsave (this
will save across reboots) enable the
zone configuration cfgenable "test_cfg"
saving the zone configuration
cfgsave
view zoning information zoneshow or
cfgshow
If you
want you can
create alias
for
zone members as
well with "alicreate" and use
cfgadd command to add zones to the active configuration.
DMX-4 Interview
Questions
· Explain Rule 17 in DMX?
The Rule of
17 is to make sure that redundancy is in place so
that the host does
not lose access in
case of a FA/DA director failure. The
director cage of
DMX can have
16 director cards numbering from 1-16. Two
director cards are paired
in such
a way that the total adds
up to 17. Example when
a host is connected/lun
is mapped
to the FA
it is mapped to directors
1 and 16 or to directors 10 and 7.
· What are the Management
Tools for DMX?
CLI -- Solution
Enabler various version depending on the Enginuity code
GUI -- SMC (Symmetrix Management
console)
·· How do you
calculate number of cylinders for
50GB LUN? A cylinder
is roughly 1 mb in
size
and 0.937mb to be precise
· What is
the maximum hyper
size
in DMX-4?
60Gb and in case of
Vmax 240Gb
· How many hypers can create in
a Single disk?
255 and in case of
Vmax 512
· How many members can contain
in one meta? Max 255 members
· How many LUN IDs
available per
port?
Technically speaking 2048. Per port
pair 4096, however this is
flexible meaning either
one
can have all the
4096 devices or 2048
each or any combination
which does not
exceed 4096. However this
is not a good practice.
· What Dynamic LUN addressing?
Once the
lun id on the port crosses
255 the host will not
be able to see the lun and
hence lun offset has to be used which has
to be implemented carefully if
not would
lead to host losing access to devices(luns). In
order to overcome this dynamicl
lun addressing is used in which the luns are numbered in the ascending order to the Host
HBA
· How do you add a new member to the
existing Meta?
using the add command
add dev 1234 to meta 4567 and
then run the symconfigure command.
· What is stripping
and what is Concatenating?
· What are the DMX-4
supported
disk types, no. of disks and
maximum
capacity? FC,SATA.
SSD is not supported. Capacity and
number of disks vary from configuration to configuration.
· Briefly explain
the DMX-4 supported Device types?
· What are the RAID levels
DMX-4
Supports? RAID 0 -unprotected
RAID 1 - 2-way Mirror
RAID 5
RAID 6
RAID 10 - 2 way Mirror Meta (Striped)
· What are Vault drives and
Hot Spare?
· What is
Preview,
Prepare and Commit while using Symconfigure command? Preview - verifies the
command syntax
Prepare - ensured
that sufficient system resources are avialble and also
checks for
any existing
locks
Commit- commits the
configuration.
This can be run directly as it performs both the Preview and
prepare actions
as well.
· How do you check
the failed disks in the Symmetrix Array?
symdisk list -failed
or symdev list -servcie_state failed
and then run a symdev show on that device
· What are the service states of a device
RW
NR Write_disabled
· How do you reserve the devices?
using reserve dev and
then running the symconfigure command
· What is Tiering and how
do you create the
Disk Groups
Tiering is
the
process of grouping the
disks based on their size, speed
and Technology (Tier
consisting of 1TB SATA or
400GB FC 10K Disks)
· How do you check
the free space by Disk group and Array as
whole?
symconfigure list -freespace or more accurate is symdisk
list
-dskgrp_summary
· Host is unable to see the storage,
what
may be the problem?
1. Zoning/masking not done
2. Correct Flags not set at the FA level
3. HBA does not have correct driver or firmware
4. Multipathing issues
5. Lun offset
might not have been
done in case of old
DMX
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