OpenVMS VMS721_SHADOWING-V0500 Alpha V7.2-1 Shadowing ECO Summary
TITLE: OpenVMS VMS721_SHADOWING-V0500 Alpha V7.2-1 Shadowing ECO Summary
Modification Date: 24-JAN-2001
Modification Type: Updated Kit Supersedes VMS721_SHADOWING-V0400
NOTE: An OpenVMS saveset or PCSI installation file is stored
on the Internet in a self-expanding compressed file.
For OpenVMS savesets, the name of the compressed saveset
file will be kit_name.a-dcx_vaxexe for OpenVMS VAX or
kit_name.a-dcx_axpexe for OpenVMS Alpha. Once the OpenVMS
saveset is copied to your system, expand the compressed
saveset by typing RUN kitname.dcx_vaxexe or kitname.dcx_alpexe.
For PCSI files, once the PCSI file is copied to your system,
rename the PCSI file to kitname-dcx_axpexe.pcsi, then it can
be expanded by typing RUN kitname-dcx_axpexe.pcsi. The resultant
file will be the PCSI installation file which can be used to install
the ECO.
Copyright (c) Compaq Computer Corporation 2000. All rights reserved.
OP/SYS: OpenVMS Alpha
COMPONENT: Volume Shadowing
SOURCE: Compaq Computer Corporation
ECO INFORMATION:
ECO Kit Name: VMS721_SHADOWING-V0500
DEC-AXPVMS-VMS721_SHADOWING-V0500--4.PCSI
ECO Kits Superseded by This ECO Kit: VMS721_SHADOWING-V0400
VMS721_SHADOWING-V0300
VMS721_SHADOWING-V0200
VMS721_SHADOWING-V0100
ECO Kit Approximate Size: 5776 Blocks
Kit Applies To: OpenVMS Alpha V7.2-1
System/Cluster Reboot Necessary: Yes
Rolling Re-boot Supported: Yes
Installation Rating: INSTALL_2
2 - To be installed on all systems running
the listed version(s) of OpenVMS and
using the following feature(s):
SHADOWING
Kit Dependencies:
The following remedial kit(s) must be installed BEFORE
installation of this kit:
VMS721_UPDATE-V0100
VMS721_PCSI-V0100
In order to receive all the corrections listed in this
kit, the following remedial kits should also be installed:
None
ECO KIT SUMMARY:
An ECO kit exists for Shadowing on OpenVMS Alpha V7.2-1. This kit
addresses the following problems:
Problems Addressed in VMS721_SHADOWING-V0500:
o Correction for DCL SHOW display errors.
After the VMS721_SHADOWING-V400 kit has been installed, a
user-mode ACCVIO or formatting display errors may occur with
various DCL SHOWs (e.g., SHOW DEVICE, SHOW MEMORY,SHOW
TERMINAL, SHOW WORK, SHOW NET).
Images Affected: [SYSMSG]CLIUTLMSG.EXE
Problems Addressed in VMS721_SHADOWING-V0400:
o The PCSI generation number on the SYS$SHDRIVER.EXE was missing
a digit, causing the image to not install over the previous
SYS$SHDRIVER.EXE image.
Images Affected: [SYS$LDR]SYS$SHDRIVER.EXE
New Functionality Included in the VMS721_SHADOWING-V0300 Kit:
o This kit contains new command features intended for use in
OpenVMS clusters that span multiple sites. An example of how
to apply the new commands will be found after they are
described.
+ DISMOUNT
1. /FORCE_REMOVAL ddcu:
If connectivity to a device has been lost and the
virtual unit is in mount verification, this switch
causes the member to be expelled immediately from the
shadow set. If you omit this qualifier, the device
is not dismounted until mount verification completes.
Note, that this qualifier cannot be used in conjunction
with the /POLICY=MINICOPY (=OPTIONAL) qualifier.
The device specified must be a member of a shadow set
that is mounted on this node.
+ SET DEVICE
1. /FORCE_REMOVAL ddcu:
If connectivity to a device has been lost and the
virtual unit is in mount verification, this qualifier
causes the member to be expelled from the shadow set
immediately.
If the shadow set is not currently in mount
verification, no immediate action is taken. If
connectivity to a device has been lost but the virtual
unit is not in mount verification, this qualifier lets
you flag the member to be expelled from the shadow
set, as soon as it does enter mount verification.
The device specified must be a member of a shadow set
that is mounted on this node.
2. /MEMBER_TIMEOUT=xxxxxx ddcu:
Specifies the time out value to be used for a member
of a shadow set.
The value supplied by this qualifier overrides the
SYSGEN parameter SHADOW_MBR_TMO for this specific
device. The value can be different for different
members of the same shadow set.
The valid range for xxxxxx is 1 to 16,777,215 seconds.
The device specified must be a member of a shadow set
that is mounted on this node.
3. /MVTIMEOUT=yyyyyy DSAnnnn:
Specifies the mount verification time out value to be
used for this virtual unit.
The value supplied by this qualifier overrides the
SYSGEN parameter MVTIMEOUT for this specific virtual
unit.
The valid range for yyyyyy is 1 to 16,777,215 seconds.
The device specified must be a virtual unit that is
mounted on this node.
4. /READ_COST=zzz ddcu:
The valid range for zzz is 1 to 4,294,967,295 units.
The device specified must be a member of a virtual
unit that is mounted on this node.
This qualifier allows you to modify the default 'cost'
assigned to each member of a virtual unit, so that
reads are biased or prioritized toward one member
versus another.
The shadowing driver assigns default READ_COST values
to shadow set members when each member is initially
mounted. The default value depends on the device
type, and its configuration relative to the system
mounting it. There are default values for a DECRAM
device; a directly connected device in same physical
location; a directly connected device in a remote
location; a DECram served device; and for other served
devices.
The value supplied by this qualifier overrides the
default assignment. The shadowing driver adds the
current queue depth of the shadow set member to the
READ_COST value and does the read operation to the
member with the lowest value.
Different systems in the cluster can assign different
costs to each shadow set member. Reads requested for
virtual units from a system at Site 1 are performed
from a member that is also at Site 1. Reads requested
for the same virtual unit from Site 2 can read from
the member located at Site 2.
If the /SITE command qualifier has been specified, the
shadowing driver will take site values into account,
when it assigns default READ_COST values. Note, that
to have the shadowing driver determine if a device is
in the category of "directly connected device in a
remote location," the /SITE command qualifier must be
have been applied to both the virtual unit and that
device.
5. /SITE={nnn, logical_name} {ddcu: DSAnnnn:}
Qualifier indicates to the shadowing driver the site
location of the shadow set member or of the virtual
unit. Prior to using this qualifier, you may define
the site location in the SYLOGICALS.COM command
procedure, to simplify its use.
The valid range for nnn is 1 through 255.
The following example shows the site locations defined,
followed by the use of the /SITE qualifier:
$ DEFINE/SYSTEM/EXEC ZKO 1
$ DEFINE/SYSTEM/EXEC LKG 2
$!
$! At the ZKO site ...
$ MOUNT/SYSTEM DSA0/SHAD=($1$DGA0:,$1$DGA1:) TEST
$ SET DEVICE/SITE=ZKO DSA0:
$!
$! At the LKG site ...
$ MOUNT/SYSTEM DSA0/SHAD=($1$DGA0,$1$DGA1) TEST
$ SET DEVICE/SITE=LKG DSA0:
$!
$! At both sites, the following would be used:
$ SET DEVICE/SITE=ZKO $1$DGA0:
$ SET DEVICE/SITE=LKG $1$DGA1:
6. /COPY_SOURCE {ddcu:,DSAnnnn:}
Controls whether one or both source members of a
virtual unit are used as the source for read data
during full copy operations, when a third member is
added to the virtual unit. This only affects copy
operations that do not use DCD operations.
HSG80 controllers have a read-ahead cache, which
significantly improves single disk read performance.
Copy operations, normally alternate reads from the two
source members, which effectively nullifies the
benefits of the read-ahead cache.
This qualifier lets you force all reads from a single
source member for the copy operation.
If the virtual unit is specified, then all reads for
full copy operations will be performed from whichever
disk is the current 'master' member, regardless of
physical location of the disk.
If a member of the virtual unit is specified, then
that member will be used as the source of all copy
operations. This allows you to choose a local source
member, rather than a remote master member.
7. /ABORT_VIRTUAL_UNIT DSAnnnn:
To use this qualifier, the virtual unit must be in
mount verification. When you specify this qualifier,
the virtual unit aborts mount verification immediately
on the node from which the qualifier is issued. This
qualifier is intended to abort mount verification when
it is known that the unit cannot be recovered. Note,
that after this command completes, that the virtual
unit must still be dismounted using the following
command:
DISMOUNT/ABORT DSAnnnn
o Use of the new DISMOUNT and SET command qualifiers.
The following diagram depicts a typical multi-site cluster
using fibre channel, and it will be used to illustrate what
steps need to be taken to manually recover one site, when the
site-to-site storage interconnect fails. Note that with
current Fibre Channel support, neither site can use the MSCP
server to regain a path to the DGA devices.
To prevent the shadowing driver from automatically recovering
virtual units, from connection-related failures, two steps
must be taken prior to any failure occurring:
1. Every device that is a member of a multi-site shadow set
must have its time out set to a very high value, using the
$ SET DEVICE /MEMBER_TIMEOUT= x ddcu: command. Use of
this command will override the SHADOW_MBR_TMO value, which
would normally be used for a shadow set member. A value
for x of 259200 would be a seventy-two hour wait time.
2. Every multi site virtual unit will also have to have its
mount verification time out raised to a high value, using
the $ SET DEVICE /MVTIMEOUT = y command. The "y" value
should always be greater than the "x" value. Use of this
command will override the MVTIMEOUT value, which would
normally be used for the virtual unit. A value for y of
259260 would be a seventy-three hour wait time.
3. Every virtual unit and every shadow set member must have a
site qualifier. As was noted above, doing so will ensure
that the read cost is correctly set. The other critical
factor in doing this involves three member shadow sets.
When they are being used, the site qualifier will ensure
that the master member of the shadow set will be properly
maintained.
In this example, DSA42 is made up of $1$DGA1000 and $1$DGA2000
<><><><><><><><><><><> LAN <><><><><><><><><><><>
Site A Site B
| |
F.C. SWITCH <><><><> XYZZY <><><><> F.C. SWITCH
| |
HSG80 <><> HSG80 HSG80 <><> HSG80
| |
$1$DGA1000 --------- DSA42 --------- $1$DGA2000
This diagram illustrates that systems at Site A or Site B have
direct access to all devices at both sites via Fibre Channel
connections. XYZZY is a theoretical point between the two
sites. If that point were to break, each site could access
different "local" members of DSA42 without error. For the
purpose of this example, Site A will be the sole site chosen
to retain access to the virtual unit. The following actions
must be taken, as shown, to recover the virtual unit at that
site.
On Site A:
$ DISMOUNT /FORCE_REMOVAL= $1$DGA2000:
Once that command has completed, the virtual unit will be
available for use at site A, only.
On Site B:
$ SET DEVICE /ABORT_VIRTUAL_UNIT DSA42:
Once the command completes, the virtual unit status will be
MntVerifyTimeout. Next, issue the following command to free
up the virtual unit:
$ DISMOUNT/ABORT DSA42:
These steps need to be taken for all affected multi-site
virtual units.
Problems Addressed in VMS721_SHADOWING-V0300:
o An INVEXCPETN crash occurs in SHIN$RESTORE_WLE_ENTRY when
a write completes to a multi-member shadowset.
Images Affected: [SYS$LDR]SYS$SHDRIVER.EXE
o A SHADDETICON occurs after removing or adding a shadowset
member.
Images Affected: [SYS$LDR]SYS$SHDRIVER.EXE
o The removal of the master member of a shadowset can cause
data corruption.
Images Affected: [SYS$LDR]SYS$SHDRIVER.EXE
o The system crashes when SS$_VALNOTVALID errors occur in
MERGE_SIGNAL.
Images Affected: [SYS$LDR]SYS$SHDRIVER.EXE
o SHOW LOGICAL returns a %LIB-F-INSVIRMEM error.
Images Affected: [SYS$LDR]SHOW.EXE
Problems Addressed in VMS721_SHADOWING-V0200:
o Multipath secondary UCBs cannot be shadow set members. The
multipath disk would be immediately removed from the shadow
set and an OPCOM message would be issued. Since MOUNT retries
this operation a number of times, even with /NOASSIST, the
failure would be repeated a number of times.
Images Affected: [SYS$LDR]SYS$SHDRIVER.EXE
o Disabling a FibreChannel cascade connection corrupts a
shadowset member. When the cascade connection is broken, two
nodes can only see their local FC device. They enter
Mountverifaction. One node will throw out its remote member
and continue using the last member. The other node will then
throw out its remote member, i.e., the disk that has just been
used by the first node. This causes the first node to have
zero members and the second node continues with a member that
did not get the last set of writes.
Images Affected: [SYS$LDR]SYS$SHDRIVER.EXE
o Disabling a FibreChannel cascade connection results in an
INVEXCPTN crash.
Images Affected: [SYS$LDR]SYS$SHDRIVER.EXE
o The SHADOWSET goes MOUNTVERIFYTIMEOUT and cannot be remounted.
The process attempting the remount hangs.
Images Affected: [SYS$LDR]SYS$SHDRIVER.EXE
o The Master Member SCB hangs until MVTIMEOUT expires.
Images Affected: [SYS$LDR]SYS$SHDRIVER.EXE
Problems Addressed in VMS721_SHADOWING-V0100:
o When a copy operation that interrupts a merge operation is
terminating, it finds that there are no members marked for the
merge and the thread crashes the system with a SHADDETINCON
bug check.
Images Affected:
- [SYS$LDR]SYS$SHDRIVER.EXE
- [SYSEXE]SHADOW_SERVER.EXE
o SHOW DEVICES shows zero percent merged status although the
shadow set status does not indicate that a merge is required.
Images Affected:
- [SYS$LDR]SYS$SHDRIVER.EXE
- [SYSEXE]SHADOW_SERVER.EXE
o Bit 16 in SHADOW_SYS_DISK can be set by the user to eliminate
using remote members of the shadowset for reads. Occasionally,
use of bit 16 fails to eliminate remote members from being used.
Images Affected:
- [SYS$LDR]SYS$SHDRIVER.EXE
- [SYSEXE]SHADOW_SERVER.EXE
o A CPUSPINWAIT bug check can occur if the read of the SCB of
a shadow set member cannot pass the checksum test.
Images Affected:
- [SYS$LDR]SYS$SHDRIVER.EXE
- [SYSEXE]SHADOW_SERVER.EXE
o DCD (Disk Copy Data) will not always be initiated properly.
During an assisted copy operation, if the source member was
dismounted or otherwise removed from the shadow set, the
connection to the controller would not clean up correctly.
Images Affected:
- [SYS$LDR]SYS$SHDRIVER.EXE
- [SYSEXE]SHADOW_SERVER.EXE
o A full copy operation that is interrupted for a mini-merge
will not complete the full copy operation correctly.
Images Affected:
- [SYS$LDR]SYS$SHDRIVER.EXE
- [SYSEXE]SHADOW_SERVER.EXE
o Typing incorrect commands results in a system crash.
Images Affected:
- [SYS$LDR]SYS$SHDRIVER.EXE
- [SYSEXE]SHADOW_SERVER.EXE
o When two disks are added to a shadowset in the same mount
command, the copies are done sequentially instead of in
parallel. This causes the copies to take twice as long as
they should.
Images Affected:
- [SYS$LDR]SYS$SHDRIVER.EXE
- [SYSEXE]SHADOW_SERVER.EXE
INSTALLATION NOTES:
The images in this kit will not take effect until the system is
rebooted. If there are other nodes in the VMScluster, they must
also be rebooted in order to make use of the new image(s).
If it is not possible or convenient to reboot the entire cluster at
this time, a rolling re-boot may be performed.
Install this kit with the POLYCENTER Software installation
utility by logging into the SYSTEM account, and typing the
following at the DCL prompt:
PRODUCT INSTALL VMS721_SHADOWING /SOURCE=[location of Kit]
The kit location may be a tape drive, CD, or a disk directory that
contains the kit.
Additional help on installing PCSI kits can be found by typing
HELP PRODUCT INSTALL at the system prompt
All trademarks are the property of their respective owners.
This patch can be found at any of these sites:
Colorado Site
Georgia Site
Files on this server are as follows:
dec-axpvms-vms721_shadowing-v0500--4.README
dec-axpvms-vms721_shadowing-v0500--4.CHKSUM
dec-axpvms-vms721_shadowing-v0500--4.pcsi-dcx_axpexe
vms721_shadowing-v0500.CVRLET_TXT
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