Dell Unity: File Creation From Customer Application Intermittently Fails On A File System (User Correctable)
Summary: Client application reports "no space left on device" when attempting to create file(s) on a Unity File System. There is sufficient available capacity in the File System.
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Symptoms
Client applications unable to create files on Unity File System due to "no space left on device".
From Unity logs, alerts below are repeated:
From Unity logs, alerts below are repeated:
B 02/17/22 16:18:34.458 sade 8cbbd701 c4_safe_ktrace UFS: 3:[nas_server] DuchNC::splitBucket, allocDuchBlock return error at line(7077), fsid=536871238, ino=15527624, hash=0x50f93a0 B 02/17/22 16:18:34.458 sade 8cbbd701 c4_safe_ktrace UFS: 3:[nas_server] i_visibleSize=8589926400, extblkno=8388600, base->depthAndNXHB=0x15000000, error=NoSpace
Cause
Number of files / sub directories per directory exceed recommended counts for a Unity file system.
Within a Unity file system, each directory has its own independent DUCH (DOS UNIX CIFS HASH) - MPD (Multi-Protocol Directory) service, index/allocated blocks (on disk layout to store directory structure), max size 8 GiB (hard coded, not configurable).
Intermittent Application file creation failures is due to DUCH capacity limitations. DUCH has several hashes, each of these hashes can extend and grab more blocks as they grow. When DUCH utilization reaches max size, if the file is written into one of the DUCH hashes that is full and must extend it will fail, if it is written into one of the hashes that has free space it will succeed.
File creation fails due to high hash collision, DUCH reached max size and no hash can be allocated.
Within a Unity file system, each directory has its own independent DUCH (DOS UNIX CIFS HASH) - MPD (Multi-Protocol Directory) service, index/allocated blocks (on disk layout to store directory structure), max size 8 GiB (hard coded, not configurable).
Intermittent Application file creation failures is due to DUCH capacity limitations. DUCH has several hashes, each of these hashes can extend and grab more blocks as they grow. When DUCH utilization reaches max size, if the file is written into one of the DUCH hashes that is full and must extend it will fail, if it is written into one of the hashes that has free space it will succeed.
File creation fails due to high hash collision, DUCH reached max size and no hash can be allocated.
Resolution
To avoid this scenario, adhere to documented limitations for file system directory / file counts - https://elabnavigator.dell.com/vault/pdf/EMC_Unity_ESSM.pd
Affected Products
Dell EMC Unity, Dell Unity 300, Dell EMC Unity 300F, Dell EMC Unity 350F, Dell EMC Unity 400, Dell EMC Unity 400F, Dell EMC Unity 450F, Dell EMC Unity 500, Dell EMC Unity 500F, Dell EMC Unity 550FProducts
Dell EMC Unity 600, Dell EMC Unity 600F, Dell EMC Unity 650F, Dell EMC Unity FamilyArticle Properties
Article Number: 000196796
Article Type: Solution
Last Modified: 13 أيار 2026
Version: 6
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