[vadblm]

8% резервируется. »

Так и есть по умолчанию. Изменить размер резерва можно при помощи tunefs -m.

-m minfree Specify the percentage of space held back from normal users; the minimum free space threshold. The default value used is 8%. Note that lowering the threshold can adversely affect perfor- mance: +o Settings of 5% and less force space optimization to always be used which will greatly increase the overhead for file writes. +o The file system's ability to avoid fragmentation will be reduced when the total free space, including the reserve, drops below 15%. As free space approaches zero, throughput can degrade by up to a factor of three over the performance obtained at a 10% threshold. If the value is raised above the current usage level, users will be unable to allocate files until enough files have been deleted to get under the higher threshold.