Both are pretty much the same in size: Code: Name: 19044.1288.211006-0501.21h2_release_svc_refresh_CLIENTBUSINESS_VOL_x64FRE_en-us.esd Size: 3798347648 bytes (3622 MiB) CRC32: 1084C53B CRC64: 46DE15B4061836FC SHA256: b5b83a0051f1c56815551c9dbac1526e83a0264debdd7ced9969cda879256866 SHA1: 51ed98ca2d880da15b1a578e03db589c4a193006 BLAKE2sp: c0457fd7513180e5fdb8462fe30c41bde8cbd9560d05e1b7bd8a04764787c82a Converted to ISO with install.esd and all available indexes/SKUs: Code: ============================================================ Running ESD -> ISO v63 ============================================================ ============================================================ Checking ESD Info . . . ============================================================ ============================================================ Creating Setup Media Layout . . . ============================================================ ============================================================ Creating boot.wim . . . ============================================================ Using LZX compression with 16 threads Archiving file data: 884 MiB of 884 MiB (100%) done Using LZX compression with 16 threads Archiving file data: 126 MiB of 126 MiB (100%) done ============================================================ Creating install.esd . . . ============================================================ Using LZMS compression with 1 thread Archiving file data: 8566 MiB of 8566 MiB (100%) done Using LZMS compression with 1 thread Archiving file data: 269 MiB of 269 MiB (100%) done Using LZMS compression with 1 thread Archiving file data: 140 MiB of 140 MiB (100%) done Using LZMS compression with 1 thread Archiving file data: 133 MiB of 133 MiB (100%) done Using LZMS compression with 1 thread Archiving file data: 151 MiB of 151 MiB (100%) done Using LZMS compression with 1 thread Archiving file data: 144 MiB of 144 MiB (100%) done ============================================================ Creating ISO . . . ============================================================ OSCDIMG 2.56 CD-ROM and DVD-ROM Premastering Utility Copyright (C) Microsoft, 1993-2012. All rights reserved. Licensed only for producing Microsoft authorized content. Scanning source tree (500 files in 41 directories) Scanning source tree complete (906 files in 86 directories) Computing directory information complete Image file is 4363845632 bytes (before optimization) Writing 906 files in 86 directories to 19044.1288.211006-0501.21H2_RELEASE_SVC_REFRESH_CLIENTBUSINESS_VOL_X64FRE_EN-US.ISO 100% complete Storage optimization saved 25 files, 14182400 bytes (1% of image) After optimization, image file is 4351737856 bytes Space saved because of embedding, sparseness or optimization = 14182400 Done. Press 0 to exit. <> Code: Name: 19044.1706.220505-0136.21h2_release_svc_refresh_clientbusiness_vol_x64fre_en-us_03d0a0dfebf88acfce0e6f870cba95ad3b3221c9.esd Size: 3854082120 bytes (3675 MiB) CRC32: 8BE0E700 CRC64: 1B73BC75722F009B SHA256: 5bcfd51ccd9d6dc07de9456651c0188464575b4268219d8614800bba9cf4f500 SHA1: 03d0a0dfebf88acfce0e6f870cba95ad3b3221c9 BLAKE2sp: c787008e264265c4af194cef7903b5644ec261719074a73b2b514385d9001c90 Converted to ISO with install.esd and all available indexes/SKUs: Code: ============================================================ Running ESD -> ISO v63 ============================================================ ============================================================ Checking ESD Info . . . ============================================================ ============================================================ Creating Setup Media Layout . . . ============================================================ ============================================================ Creating boot.wim . . . ============================================================ Using LZX compression with 16 threads Archiving file data: 886 MiB of 886 MiB (100%) done Using LZX compression with 16 threads Archiving file data: 127 MiB of 127 MiB (100%) done ============================================================ Creating install.esd . . . ============================================================ Using LZMS compression with 1 thread Archiving file data: 8631 MiB of 8631 MiB (100%) done Using LZMS compression with 1 thread Archiving file data: 258 MiB of 258 MiB (100%) done Using LZMS compression with 1 thread Archiving file data: 128 MiB of 128 MiB (100%) done Using LZMS compression with 1 thread Archiving file data: 133 MiB of 133 MiB (100%) done Using LZMS compression with 1 thread Archiving file data: 155 MiB of 155 MiB (100%) done Using LZMS compression with 1 thread Archiving file data: 148 MiB of 148 MiB (100%) done ============================================================ Creating ISO . . . ============================================================ OSCDIMG 2.56 CD-ROM and DVD-ROM Premastering Utility Copyright (C) Microsoft, 1993-2012. All rights reserved. Licensed only for producing Microsoft authorized content. Scanning source tree (500 files in 41 directories) Scanning source tree complete (906 files in 86 directories) Computing directory information complete Image file is 4424171520 bytes (before optimization) Writing 906 files in 86 directories to 19044.1706.220505-0400.21H2_RELEASE_SVC_REFRESH_CLIENTBUSINESS_VOL_X64FRE_EN-US.ISO 100% complete Storage optimization saved 25 files, 14182400 bytes (1% of image) After optimization, image file is 4412047360 bytes Space saved because of embedding, sparseness or optimization = 14182400 Done. Press 0 to exit.