       $                               Compaq   Software Product  Description   C ___________________________________________________________________   F PRODUCT NAME:  Volume Shadowing for OpenVMS, Version 7.3  SPD 27.29.15   Note:   D This is the Software Product Description (SPD) for the following two	 products:   % o  Volume Shadowing for OpenVMS Alpha   # o  Volume Shadowing for OpenVMS VAX   C Except where specifically noted, the features described in this SPD C apply to both products. The license and part number information is  G architecture specific. Please refer to the Ordering Information section   of this SPD for further details.   DESCRIPTION   F Volume Shadowing for OpenVMS is a System Integrated Product (SIP) thatF runs on the Alpha and VAX families of processors. Volume Shadowing forE OpenVMS implements a RAID Level 1 storage strategy that provides high D data availability for disk devices by preventing data loss resultingC from media deterioration or from controller or device failure. This A strategy also prevents storage subsystem component failures from  . interrupting system or application operations.  D Volume shadowing, sometimes referred to as disk mirroring, maintainsE redundant copies of data on a collection of disks (one copy per disk) ? called a shadow set. Shadow sets consist of one, two, or three  G compatible disk volumes or shadow set members. This duplication of data D provides enhanced data availability; if data is recorded on multiple  C                                                         April, 2001        F disk volumes, it remains accessible if one volume becomes unavailable.H Disk read and write operations continue transparently with the remaining members of the shadow set.  E Because a shadow set is made up of multiple disks containing the same F data, the Volume Shadowing for OpenVMS software can read data from anyG member of the shadow set. For each read operation, the Volume Shadowing @ for OpenVMS software determines which disk to read from using anB algorithm that maximizes performance. Volume Shadowing for OpenVMS? ensures that disk write operations are duplicated on all shadow C set members. For maximum performance, Volume Shadowing for OpenVMS  I ensures that shadow set write operations are issued in parallel to shadow  set members.  E If some data on a shadow set member becomes unreadable, the shadowing F oftware can read the data from another available member. Additionally,> with DIGITAL Storage Architecture (DSA) disks, the member with@ unreadable data can be repaired by rewriting the data to viable,@ replacement areas provided on each disk. Small Computer Systems A Interface (SCSI) devices certified by Compaq for use with volume  F Shadowing support data repair. For other SCSI devices, replacement and& repair algorithms are device specific.  I OpenVMS Alpha and VAX system disks, Files-11 On-Disk Structure 2 (ODS-2), F and Files-11 On-Disk Structure 5 (ODS-5) data disks that are certified= by Compaq can be volume shadowed. For more information, refer 1 to the Hardware Requirements section of this SPD.   @ Volume Shadowing for OpenVMS implements a host-based (phase II) @ approach to shadowing disk devices. Previous versions of Volume G Shadowing for OpenVMS VAX also implemented a controller-based (phase I) D approach to disk shadowing. Phase I shadowing is no longer available
 or supported.   E For the purposes of this document, the term system refers to a single D Alpha or VAX computer that contains one or more processors. A systemD can be a standalone system or a member of an OpenVMS Cluster system.? The term OpenVMS Cluster refers to a cluster that may contain a 9 mix of Alpha systems and VAX systems configured together.   "                                  2       E Volume Shadowing for OpenVMS supports clusterwide shadowing of Compaq F Alpha SCSI, DSA, and Fibre Channel disk storage systems. Specifically, this implementation supports:   < o  HSC, HSD, HSF, HSG, HSJ, HSZ, and K.SCSI controlled disks  I o  All DSA, Fibre Channel, and Compaq Alpha SCSI adapters and controllers )    that are locally connected to a system   C o  RF-series controllers and disks connected to the Digital Storage     Systems Interconnect (DSSI)  F Volume Shadowing also supports OpenVMS MSCP served DSA, Fibre Channel,@ and Compaq Alpha SCSI disks located within any supported OpenVMS@ Cluster configuration. Compaq DECram virtual disks can be volume. shadowed only with other DECram virtual disks.  @ Volume Shadowing for OpenVMS allows shadowing of disks that are H accessible from the system on which the shadowing software is installed.G An OpenVMS system parameter enables shadowing at system initialization.    Configuration Overview  E Volume Shadowing for OpenVMS requires a minimum of one system, a disk A controller, and a disk unit that is DSA compliant, Fibre Channel  F compliant, or SCSI compliant. Although only one disk is required for aF shadow set, two or more disks are required to maintain multiple copiesC of the same data. This protects against failure or deterioration of  a single volume.  G Using two controllers provides a further guarantee of data availability D in the event that a single controller fails. OpenVMS Cluster systemsD can be configured with multiple systems, interconnects, controllers,G and disks; the resulting configurations can provide extremely high data 
 availability.         "                                  3        Shadow Set Membership   D A shadow set can have one, two, or three members. If one member of aG two-member shadow set fails, the shadow set can continue operation with  the remaining member.   I Shadow set members can be added to or removed from the shadow set without B affecting system or user operation. A disk can be removed from theG shadow set either by operator command or automatically by the shadowing K software. An inoperative disk is removed from the shadow set automatically; & operator intervention is not required.  D Adding a disk to a shadow set requires an explicit operator command.C The shadowing software ensures that data on the newly added disk is D made consistent with the other members by means of a copy operation.E Full read and write access to the shadow set continues while the copy  operation is in progress.    Transparency to the End User  @ To users and application programs, Volume Shadowing for OpenVMS H transparently combines the physical members of a given shadow set into aG single virtual unit. The shadow set virtual unit acts as a single disk. ? User or application program modifications are not necessary to  H propagate write data to shadow set members; Volume Shadowing for OpenVMSE software automatically propagates the data to all shadow set members. C Similarly, user and application read operations to the virtual disk C are transparently routed to the optimal physical shadow set member.   E Volume Shadowing for OpenVMS is invisible to application programs and J users. All commands and programming language features that address data onJ nonshadowed disks can be used unchanged to address data on shadowed disks.   Minicopy and Backup   J The minicopy operation, new for Volume Shadowing Version 7.3, is a stream-C lined copy operation. Minicopy is designed to be used in place of a D copy operation when a shadow set member is returned to a shadow set.F When a member has been removed from a shadow set (for example, to backC up that member), a write bitmap tracks the changes that are made to   "                                  4       D the shadow set in the member's absence. With minicopy, you no longerD need to remove the entire virtual unit (shadow set) to back up data.G When the member is returned to the shadow set, the write bitmap is used D to direct the minicopy operation. While the minicopy operation takesC place, the application can continue to read and write to the shadow  set.  C The new minicopy feature and its enabling technology, write bitmap, G are fully implemented for OpenVMS Alpha systems only. OpenVMS VAX nodes E can write to shadow sets which use this feature, but they can neither C create master write bitmaps nor manage them with DCL commands. In a F mixed-version cluster, remedial Volume Shadowing kits are required forE systems running earlier versions of OpenVMS in order to use minicopy.                                                       "                                  5        Multiple-Site Clusters  B OpenVMS Version 7.3 introduces new command qualifiers for the DCL B commands DISMOUNT and SET for use with Volume Shadowing. These newF command qualifiers provide disaster-tolerant support for multiple-siteF OpenVMS Cluster systems. Designed primarily for multiple-site clustersD that use Fibre Channel as a site-to-site interconnect, these command@ qualifiers can be used in other configurations as well. See more3 details in the Volume Shadowing for OpenVMS manual.   
 Compatibility   E Volume Shadowing for OpenVMS Alpha is compatible and can operate with F Volume Shadowing for OpenVMS VAX. The use of both products in a mixed-H architecture OpenVMS Cluster (Alpha and VAX machines clustered together)C can enable the sharing of data disks between Alpha and VAX systems. H However, a single system disk cannot be shared for booting between AlphaE and VAX systems in an OpenVMS Cluster because booting is architecture 	 specific.    Configuration Limits  I Volume Shadowing for OpenVMS supports a maximum of 500 disks in multiple- C member (2- or 3-member) shadow sets on a single OpenVMS Cluster. Up C to 10,000 single-member shadow sets are allowed on the same OpenVMS H Cluster or standalone system. These limits are independent of controller and device type.   Configuration Restrictions  I Controller-based Volume Shadowing for OpenVMS VAX is no longer available.   I All members of a shadow set must have the same number of physical blocks. F For example, two RA92 disk drives could form a shadow set. An RZ28 andG an RZ28B disk drive could also form a shadow set. However, a 6 gigabyte C disk and an 8 gigabyte disk could not be members of the same shadow  set.    "                                  6       J Shadow set members cannot have hardware write protection enabled. HardwareA write protection stops volume shadowing software from maintaining  identical volumes.  F Volume Shadowing for OpenVMS does not support shadow sets mounted with the /FOREIGN qualifier.   C Volume Shadowing for OpenVMS provides support for Compaq SCSI disks H and controllers on Alpha systems. Shadowing can also be used with third-D party SCSI disks that have READL (read long) and WRITEL (write long)@ commands implemented and that use the OpenVMS SCSI disk driver. L Features are restricted when SCSI disks that do not support READL and WRITELC are shadowed; disk bad-block errors resulting from the use of these : disks can cause members to be removed from the shadow set.   HARDWARE REQUIREMENTS   D Volume Shadowing for OpenVMS does not depend on specific hardware toC operate. All shadowing functions can be performed on any supported  F system. Members of a shadow set can be located on any single system orC anywhere in an OpenVMS Cluster system. There are no restrictions on G the location of shadow set members beyond the valid disk configurations D defined in the OpenVMS Operating System Software Product Description@ (SPD 25.01.xx) and the OpenVMS Cluster Software Software Product Description (SPD 29.78.xx).    Disk Controller Support   D Volume Shadowing for OpenVMS supports all disk controllers listed asF supported in the OpenVMS Operating System Software Product Description; (SPD 25.01.xx), with the exception of VAX SCSI controllers.     "                                  7      Disk Drive Support  ? Volume Shadowing for OpenVMS supports all disk drives listed as F supported in the OpenVMS Operating System Software Product Description> (SPD 25.01.xx), with the following constraints and exceptions:  I o  RF35 and RF73 disk devices must use at minimum firmware version T392F.   I o  RF36 and RF74 disk devices must use at minimum firmware version V427P.   ? o  KDM70 controllers must be at minimum microcode revision 4.3.   D o  Disks attached to a local VAX SCSI controller on VAX 4000 and VAX)    3000 series systems are not supported.    OpenVMS Cluster Environment   E Volume Shadowing for OpenVMS is fully supported in an OpenVMS Cluster H when installed on any valid and licensed configuration. Volume Shadowing@ for OpenVMS allows shadowing of disks that are locally connectedC to the Alpha or VAX system on which this software is installed. In  C addition, Volume Shadowing for OpenVMS allows a user on an OpenVMS  I system to shadow disks connected to other Alpha or VAX systems within the  OpenVMS Cluster.  2 An OpenVMS Cluster quorum disk cannot be shadowed.  J For additional information, refer to the OpenVMS Cluster Software Software# Product Description (SPD 29.78.xx).    SOFTWARE REQUIREMENTS   G Volume Shadowing for OpenVMS Version 7.3 is a System Integrated Product " that requires OpenVMS Version 7.3.  G For additional information, and minimum software and firmware revisions = for storage subsystems, refer to the OpenVMS Operating System , Software Product Description (SPD 25.01.xx).   OPTIONAL SOFTWARE   F Optional products that may be useful when running Volume Shadowing for OpenVMS include:  * o  OpenVMS Cluster Software (SPD 29.78.xx)  + o  Compaq DECram for OpenVMS (SPD 34.26.xx)   2 o  Compaq RAID Software for OpenVMS (SPD 46.49.xx)  "                                  8          GROWTH CONSIDERATIONS   H The minimum hardware and software requirements for any future version ofL this product may be different from the requirements for the current version.   DISTRIBUTION AND INSTALLATION   G Volume Shadowing for OpenVMS Version 7.3 is a System Integrated Product C that is distributed and installed with the OpenVMS operating system @ Version 7.3. Documentation for Volume Shadowing is also includedH with OpenVMS. Licenses and services are available separately as follows:   ORDERING INFORMATION  & For Volume Shadowing on OpenVMS Alpha:  * o  Software Capacity Licenses: QL-2A1A*-**  * o  Software Per-Disk Licenses: QL-2A1AA-3B  ) o  Software Product Services: QT-2A1A*-**   $ For Volume Shadowing on OpenVMS VAX:  * o  Software Capacity Licenses: QL-AB2A*-**  * o  Software Per-Disk Licenses: QL-2A1AA-3B  ) o  Software Product Services: QT-AB2A*-**   D * Denotes variant fields. For additional information about availableC licenses, services, and media, refer to the appropriate price list.         "                                  9        SOFTWARE LICENSING  C This software is furnished under the licensing provisions of Compaq 5 Computer Corporation's Standard Terms and Conditions.   # License Management Facility Support   D Volume Shadowing for OpenVMS supports the OpenVMS License Management Facility (LMF).   G Licenses for Volume Shadowing for OpenVMS are sold on either a capacity  or a per-disk basis.  E A capacity license allows a varying number of disks to be shadowed on H a single system, up to the maximum specified in the Configuration LimitsF section. When using a capacity licensing scheme in an OpenVMS Cluster,@ every system in an OpenVMS Cluster that mounts a shadow set mustC have a properly sized Volume Shadowing for OpenVMS capacity license 
 installed.  @ Alternatively, licenses are available on a per-disk basis using E concurrent user licensing. With this type of licensing, one per-disk  G license is required for every disk that may become a member of a shadow E set. The per-disk license is attached to a particular disk during the D MOUNT process. That disk can then be included in a shadow set by anyF OpenVMS Alpha or VAX member of the OpenVMS Cluster with access to that disk.   B Both methods of licensing can coexist in a single OpenVMS Cluster.  D For more information about the License Management Facility, refer toH the OpenVMS Operating System Software Product Description (SPD 25.01.xx)@ or the OpenVMS License Management Utility Manual in the OpenVMS  documentation set.  I For more information about Compaq's licensing terms and policies, contact  your local Compaq office.       "                                 10        SOFTWARE PRODUCT SERVICESp  A A variety of service options are available from Compaq. For more _. information, contact your local Compaq office.   SOFTWARE WARRANTYd  J Warranty for this software product is provided by Compaq with the purchase@ of a license for the product as defined in the Software Warranty Addendum of this SPD.p  D The previous information is valid at time of release. Please contact= your local Compaq office for the most up-to-date information.b  "  2001 Compaq Computer Corporation  C Compaq, Digital, HSC, HSJ, VAX, VMS, and the Compaq logo Registeredn$ in U.S. Patent and Trademark Office.  G Alpha, DECram, HSD, HSF, HSG, HSZ, and OpenVMS are trademarks of CompaqtC Information Technologies Group, L.P. in the United States and othero
 countries.  C All other product names mentioned herein may be trademarks of theire respective companies.   F Confidential computer software. Valid license from Compaq required forC possession, use, or copying. Consistent with FAR 12.211 and 12.212,aC Commercial Computer Software, Computer Software Documentation, and rG Technical Data for Commercial Items are licensed to the U.S. Governmente+ under vendor's standard commercial license.d  @ Compaq shall not be liable for technical or editorial errors or H omissions contained herein. The information in this document is providedE "as is" without warranty of any kind and is subject to change withouts? notice. The warranties for Compaq products are set forth in the G express limited warranty statements accompanying such products. Nothing B herein should be construed as constituting an additional warranty.    "                                 11