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I am in the process of evaluating different anti-virus on Mac OS X (Mountain Lion, Mavericks, Yosemite…). Upon running a full scan to test Sophos on a Mountain Lion Mac I witnessed a total slow down of this scan without any error, hint or explanation.

Hence I searched the standard system log file to see what this hidden problem might be coming from.

I have a lot of repeated sequences of error messages coming from decmpfs which are time related:

Aug 16 01:22:01 ••my Mac•• com.apple.backupd[54217]: Backing up to: /Volumes/••my backup volume••/Backups.backupdb
Aug 16 01:22:01 ••my Mac•• kernel[0]: /SourceCache/AppleFSCompression_kexts/AppleFSCompression-49/Compressors/Dataless/compressorType5Kext.c:532: Error: post_request error for /Volumes/••my backup volume••/Backups.backupdb/••my Mac••/2015-07-23-080243/••my Mac root volume••/.DocumentRevisions-V100/PerUID/501/2a/com.apple.documentVersions/B15D3CEE-6DAA-4EB2-AD77-B8EBD67CBD41.pages: 35
Aug 16 01:22:01 ••my Mac•• kernel[0]: decmpfs.c:1339:decmpfs_read_compressed: decmpfs_fetch_uncompressed_data err -35
Aug 16 01:22:06 ••my Mac•• com.apple.backupd[54217]: Using file event preflight for ••my Mac root volume••
Aug 16 01:22:06 ••my Mac•• com.apple.backupd[54217]: Will copy (445 KB) from ••my Mac root volume••
Aug 16 01:22:06 ••my Mac•• com.apple.backupd[54217]: Found 41 files (445 KB) needing backup
Aug 16 01:22:06 ••my Mac•• com.apple.backupd[54217]: 1.83 GB required (including padding), 5.53 GB available
Aug 16 01:22:16 ••my Mac•• kernel[0]: /SourceCache/AppleFSCompression_kexts/AppleFSCompression-49/Compressors/Dataless/compressorType5Kext.c:532: Error: post_request error for /Volumes/••my backup volume••/Backups.backupdb/••my Mac••/2015-07-23-080243/••my Mac root volume••/.DocumentRevisions-V100/PerUID/501/2a/com.apple.documentVersions/B15D3CEE-6DAA-4EB2-AD77-B8EBD67CBD41.pages: 35
Aug 16 01:22:16 ••my Mac•• kernel[0]: decmpfs.c:1339:decmpfs_read_compressed: decmpfs_fetch_uncompressed_data err -35
Aug 16 01:22:32 ••my Mac•• kernel[0]: /SourceCache/AppleFSCompression_kexts/AppleFSCompression-49/Compressors/Dataless/compressorType5Kext.c:532: Error: post_request error for /Volumes/••my backup volume••/Backups.backupdb/••my Mac••/2015-07-23-080243/••my Mac root volume••/.DocumentRevisions-V100/PerUID/501/2b/com.apple.documentVersions/025F1963-3BA9-4B0B-ADFD-4E51082CC82B.pages: 35
Aug 16 01:22:32 ••my Mac•• kernel[0]: decmpfs.c:1339:decmpfs_read_compressed: decmpfs_fetch_uncompressed_data err -35
Aug 16 01:22:37 ••my Mac•• com.apple.backupd[54217]: Copied 1379 files (462 KB) from volume ••my Mac root volume••.
Aug 16 01:22:39 ••my Mac•• com.apple.backupd[54217]: Using file event preflight for ••my Mac root volume••
Aug 16 01:22:39 ••my Mac•• com.apple.backupd[54217]: Will copy (Zero KB) from ••my Mac root volume••
Aug 16 01:22:39 ••my Mac•• com.apple.backupd[54217]: Found 6 files (Zero KB) needing backup
Aug 16 01:22:39 ••my Mac•• com.apple.backupd[54217]: 1.83 GB required (including padding), 5.53 GB available
Aug 16 01:22:43 ••my Mac•• com.apple.backupd[54217]: Copied 155 files (153 bytes) from volume ••my Mac root volume••.
Aug 16 01:22:44 ••my Mac•• com.apple.backupd[54217]: Created new backup: 2015-08-16-012243
Aug 16 01:22:44 ••my Mac•• com.apple.backupd[54217]: Starting post-backup thinning
Aug 16 01:22:44 ••my Mac•• com.apple.backupd[54217]: No post-back up thinning needed: no expired backups exist
Aug 16 01:22:44 ••my Mac•• com.apple.backupd[54217]: Backup completed successfully.

I made a research within the Apple Knowledge Base and found nothing. I found a lot of discussions about this kind of errors on Apple discussions groups. But nothing the level above discussion.

A time back analysis of my /var/log/system.log.*.bz2 shows that I never had such a kernel error within 7 days before and that the first one occured at the exact time of starting my 1st scan with Sophos.


What are these error messages caused by (Time Machine, kernel, Sophos)?

What do they mean?

  • 1
    Do you encounter such slow-downs also after disabling archive scan in Sophos? Additionally you may try to remove the temp folder Sophos uses to unarchive compressed files from being backed-up by Time Machine (i don't know if such a folder exists though, i may have to explore that). – klanomath Aug 16 '15 at 11:10
  • The "Scan: ☐ Inside archives and compredssed files" was set to off. – dan Aug 16 '15 at 14:59

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