OpenVMS Dynamic Volume Expansion

1. OpenVMS Dynamic Volume Expansion Addendum to the presentation given at the Swiss OpenVMS Technology Forum, 20.April 2004, Dübendorf

2. Dynamic Volume Expansion • WHY ? • Need to grow volume sizes with minimal impact on operations • New storage subsystems can expand the size of a unit without taking it off-line • Host Based Volume Shadowing enables volume growth via Dissimilar Device Support even if storage subsystems are unable to dynamically expand units HP corporate presentation tutorial - XP

3. Dynamic Volume Expansion • HOW ? • Determine how big this volume may ever get to make maximum use of the dynamic expansion capability • New Volume: • INIT/LIMIT=Maximum_size • Existing Volume: • SET VOLUME/LIMIT=Maximum_size • Issued one time only • Volume requires to be mounted privately • Overhead in disk space ≤ 32 MB HP corporate presentation tutorial - XP

4. Before Dynamic Volume Expansion Bitmap allows to address UCB$L_MAXBLOCK/Cluster_Size Clusters on the disk Physical Disk Size UCB$L_MAXBLOCK “Total blocks” HP corporate presentation tutorial - XP

5. DVE – Volume preparation Bitmap allows to address UCB$L_MAXBLOCK/Cluster_Size Clusters on the disk $ set volume/limit -- For existing volumes -- The volume requires to be mounted privately $ initialize/size=n -- For new volumes -- Set the current Logical Volume Size of the volume -- Defaults to UCB$L_MAXBLOCK Volume may be a shadow set ora single disk Physical Disk Size UCB$L_MAXBLOCK “Total blocks” HP corporate presentation tutorial - XP

6. DVE – Volume preparation Extended Bitmap allows addressingup to “Expansion size limit”bitmap size ≤ 65’535 blocks $ set volume/limit VMS extends bitmap and sets up „Expansion size limit“ Maximum Expansion “Expansion size limit” (≤ 1 TB) Physical Disk Size UCB$L_MAXBLOCK “Total blocks” HP corporate presentation tutorial - XP

7. DVE – Volume preparation Extended Bitmap allows addressingup to “Expansion size limit”bitmap size ≤ 65’535 blocks $ set volume/limit VMS extends bitmap and sets up „Expansion size limit“VMS sets up „Logical VolumeSize“ Current size (usable space) SCB$L_VOLSIZE “Logical Volume Size”≤“Total blocks” Maximum Expansion “Expansion size limit” (1 TB) Physical Disk Size UCB$L_MAXBLOCK “Total blocks” HP corporate presentation tutorial - XP

8. DVE – Use prepared volume Extended Bitmap allows addressingup to “Expansion size limit”bitmap size ≤ 65’535 blocks Prepared volume is mounted as required by the application (shared, clusterwide) and in use Volume may be a shadow setor a single disk Current size (usable space) SCB$L_VOLSIZE “Logical Volume Size”≤“Total blocks” Maximum Expansion “Expansion size limit” (1 TB) Physical Disk Size UCB$L_MAXBLOCK “Total blocks” HP corporate presentation tutorial - XP

9. DVE – Extend capacity in storage subsystem Extended Bitmap allows addressingup to “Expansion size limit”bitmap size ≤ 65’535 blocks Use storage subsystem specificcommands to increase capacityof corresponding unit (Repeat for all units representingmembers of the shadow set) Current size (usable space) SCB$L_VOLSIZE “Logical Volume Size”≤“Total blocks” Maximum Expansion “Expansion size limit” (1 TB) Physical Disk Size UCB$L_MAXBLOCK “Total blocks” HP corporate presentation tutorial - XP

10. DVE – Extend capacity in OpenVMS Extended Bitmap allows addressingup to “Expansion size limit”bitmap size ≤ 65’535 blocks $ set volume/size Current size (usable space) SCB$L_VOLSIZE “Logical Volume Size”≤“Total blocks” Maximum Expansion “Expansion size limit” (1 TB) Physical Disk Size UCB$L_MAXBLOCK “Total blocks” HP corporate presentation tutorial - XP

11. DVE – Extend capacity in OpenVMS Extended Bitmap allows addressingup to “Expansion size limit”bitmap size ≤ 65’535 blocks $ set volume/size VMS checks new capacity(Checks all members if volumeis a shadow set) Current size (usable space) SCB$L_VOLSIZE “Logical Volume Size”≤“Total blocks” Maximum Expansion “Expansion size limit” (1 TB) Physical Disk Size UCB$L_MAXBLOCK “Total blocks” HP corporate presentation tutorial - XP

12. DVE – Extend capacity in OpenVMS Extended Bitmap allows addressingup to “Expansion size limit”bitmap size ≤ 65’535 blocks $ set volume/size VMS checks new capacity updates UCB$L_MAXBLOCK (if shadow set: new value is smallest of all member values) Current size (usable space) SCB$L_VOLSIZE “Logical Volume Size”≤“Total blocks” Maximum Expansion “Expansion size limit” (1 TB) Physical Disk Size UCB$L_MAXBLOCK “Total blocks” HP corporate presentation tutorial - XP

13. DVE – Extend capacity in OpenVMS Extended Bitmap allows addressingup to “Expansion size limit”bitmap size ≤ 65’535 blocks $ set volume/size VMS checks new capacity updates UCB$L_MAXBLOCKupdates SCB$L_VOLSIZE Current size (usable space) SCB$L_VOLSIZE “Logical Volume Size”≤“Total blocks” Maximum Expansion “Expansion size limit” (1 TB) Physical Disk Size UCB$L_MAXBLOCK “Total blocks” HP corporate presentation tutorial - XP

14. DVE – Extend capacity in OpenVMS Extended Bitmap allows addressingup to “Expansion size limit”bitmap size ≤ 65’535 blocks The extended volume is now available Current size (usable space) SCB$L_VOLSIZE “Logical Volume Size”≤“Total blocks” Maximum Expansion “Expansion size limit” (1 TB) Physical Disk Size UCB$L_MAXBLOCK “Total blocks” HP corporate presentation tutorial - XP

15. DVE Qualifiers – New volumes • INITIALIZE/SIZE [=n] • Specifies the amount of disk space that is usable for the file system • Sets the Logical Volume Size of the volume, where • LogVolSize = min(n,UCB$L_MAXBLOCK) • Defaults to UCB$L_MAXBLOCK • Unit is 512 byte blocks HP corporate presentation tutorial - XP

16. DVE Qualifiers – Existing volumes • SET VOLUME/LIMIT [=n] • Must be done while MOUNTED privately • Prepares a volume for future expansion (with /SIZE) • extends or moves the bitmap to accomodate expansion potential • cluster_size ≥ 8 expansion limit = 1TB • cluster_size < 8  expansion limit = 65535*4096*CLS • 65535 -- Maximum size of BITMAP.SYS in 512 byte blocks • 4096 -- Number of 512 byte blocks per cluster • CLS -- Cluster-Size, number of bits in each 512 byte block • one bit represents one cluster • Needs to be issued only once per volume • Does not change the clustersize • Does not change the logical volume size HP corporate presentation tutorial - XP

17. DVE Qualifiers – Existing volumes • SET VOLUME/SIZE [=nnn] • May be done online with applications active • Specifies the amount of disk space that is usable for the file system • Sets the Logical Volume Size of the volume • greater than the current logical volume size and • less than or equal to the physical size of the disk or the expansion limit (specified by /LIMIT), whichever is smaller • If the value of SIZE is omitted • the usable space is increased to the physical size of the disk or the expansion limit, whichever is smaller HP corporate presentation tutorial - XP

18. DVE Qualifiers – Existing volumes • SET VOLUME/SIZE [=nnn], Details: • Checks physical volume size (it may have changed) • If volume is a shadow set, all members are checked • Updates UCB$L_MAXBLOCK • If volume is a shadow set • the individual UCB$L_MAXBLOCK values are updated • new UCB$L_MAXBLOCK of the shadow set is set to the smallest member’s UCB$L_MAXBLOCK • Sets the current logical volume to the size specified, but • Will not extend beyond UCB$L_MAXBLOCK or the capacity of the storage bitmap (expansion size limit) • Will not reduce the current size of the mounted volume • Updates SCB$L_VOLSIZE • Space available to the file system HP corporate presentation tutorial - XP

19. DVE more information • Show Device/Full • TOTAL BLOCKS • actual size of device or storage container • derived from UCB$L_MAXBLOCK • Logical Volume Size • derived from SCB$L_VOLSIZE • Expansion size limit • $GETDVI and F$GETDVI support for new fields HP corporate presentation tutorial - XP

20. DDS & DVE (for fixed size units) Storage Subsystem is not able to extend capacity of units 2-member Shadow set Current size (usable space) SCB$L_VOLSIZE “Logical Volume Size” Maximum Expansion “Expansion size limit” Physical Disk Size UCB$L_MAXBLOCK “Total blocks” HP corporate presentation tutorial - XP

21. DDS & DVE (for fixed size units) Storage Subsystem is not able to extend capacity of units Add largerdisk toform a3-dissimilarmember Shadow set Current size (usable space) SCB$L_VOLSIZE “Logical Volume Size” Maximum Expansion “Expansion size limit” Physical Disk Size UCB$L_MAXBLOCK “Total blocks” of smaller disk HP corporate presentation tutorial - XP

22. DDS & DVE (for fixed size units) Storage Subsystem is not able to extend capacity of units Keep one smaller member to preserve redundancy Remove smallermember to form2-dissimilarmembershadow set Current size (usable space) $ set volume/size=n SCB$L_VOLSIZE “Logical Volume Size” Maximum Expansion “Expansion size limit” Physical Disk Size UCB$L_MAXBLOCK “Total blocks” of smaller disk HP corporate presentation tutorial - XP

23. DDS & DVE (for fixed size units) Storage Subsystem is not able to extend capacity of units Add 2nd large member to form3-dissimilarmembershadow set Current size (usable space) SCB$L_VOLSIZE “Logical Volume Size” Maximum Expansion “Expansion size limit” Physical Disk Size UCB$L_MAXBLOCK “Total blocks” of larger disk HP corporate presentation tutorial - XP

24. DDS & DVE (for fixed size units) Storage Subsystem is not able to extend capacity of units Remove smallmember Current size (usable space) $ set volume/size=n SCB$L_VOLSIZE “Logical Volume Size” Maximum Expansion “Expansion size limit” Physical Disk Size UCB$L_MAXBLOCK “Total blocks” HP corporate presentation tutorial - XP

25. DDS & DVE (for fixed size units) Storage Subsystem is not able to extend capacity of units Adjust volumesize(set volume/size) Current size (usable space) $ set volume/size=n SCB$L_VOLSIZE “Logical Volume Size” Maximum Expansion “Expansion size limit” (1 TB) Physical Disk Size UCB$L_MAXBLOCK “Total blocks” HP corporate presentation tutorial - XP

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