IBM XIV Storage System Copy Services and Migration

When an SVC volume is created we normally specify a size in GiB (binary GB). For instance,Example 8-48 creates a 10 GiB Vdisk in Mdisk group 1.Example 8-48 Create a transitional VDisksvctask mkvdisk -mdiskgrp 1 -iogrp 0 -name migrateme -size 10 -unit gbNow to make a matching XIV volume we can either make an XIV volume that is larger thanthe source VDisk or one that is exactly the same size. The easy solution is to create a largervolume. Because the XIV creates volumes in 16 GiB portions (that display in the GUI asrounded decimal 17 GB chunks), we could create a 17 GB LUN using the XIV and then mapit to the SVC (in this example the SVC host is defined by the XIV as svcstgdemo) and use thenext free LUN ID, which in Example 8-49 is LUN ID 12 (it is different every time).Example 8-49 XIV commands to create transitional volumesvol_create size=17 pool="SVC_MigratePool" vol="ImageMode"map_vol host="svcstgdemo" vol="ImageMode" lun="12"The drawback of using a larger volume size is that we eventually end up using extra space.So it is better to create a volume that is exactly the same size. To do this we must know thesize of the VDisk in bytes (by default the SVC shows the VDisk size in GiB, even though itsays GB). In Example 8-50 we first choose to display the size of the VDisk in GB.Example 8-50 Displaying a VDisk size in GBIBM_2145:SVCSTGDEMO:admin>svcinfo lsvdisk -filtervalue mdisk_grp_id=1id name status mdisk_grp_id mdisk_grp_name capacity6 migrateme online 1 MGR_MDSK_GRP 10.00GBExample 8-51 displays the size of the same VDisk in bytes.Example 8-51 Displaying a VDisk size in bytesIBM_2145:SVCSTGDEMO:admin>svcinfo lsvdisk -filtervalue mdisk_grp_id=1 -bytesid name status mdisk_grp_id mdisk_grp_name capacity6 migrateme online 1 MGR_MDSK_GRP 10737418240Now that we know the size of the source VDisk in bytes, we can divide this by 512 to get thesize in blocks (there are always 512 bytes in a standard SCSI block). 10,737,418,240 bytesdivided by 512 bytes per block is 20,971,520 blocks. This is the size that we use on the XIV tocreate our image mode transitional volume.Example 8-52 shows an XCLI command run on an XIV to create a volume using blocks.Example 8-52 Create an XIV volume using blocksvol_create size_blocks=20971520 pool="SVC_MigratePool" vol="ImageBlocks"268 IBM XIV Storage System: Copy Services and Migration