phd_ivo@gsbacd.uchicago.edu (06/21/89)
******************************************************************************* Could someone please explain to me why a 256MB formatted OD only shows up with 236MB? Also, could someone please tell me what the sector size on both the OD and the harddisks are, please? /ivo welch phd_ivo@gsbacd.uchicago.edu
carlson@mrcnext.cso.uiuc.edu (06/22/89)
Part of the disk space is used for i-nodes (control info). Also, 10% is reserved, for efficiency and for emergencies. (No specific area of the disk is set aside, the system just keeps at least 10% free at all times.) The 236MB is what's left for general users, and this is the 100% usage figure from df(1). Only the superuser can use reserved space, and could run usage up to 110%. The sector size is (usually) 1k. A storage block is 8k, with 1k fragments. See fs(5), fstab(5), and /etc/fstab. Example: # @(#)disktab 4.11 (Berkeley) 5/31/86 # Disk geometry and partition layout tables. # Key: # ss sector size -- MUST ALWAYS BE DEV_BSIZE (1024) FOR NOW # b[a-h] partition block sizes in bytes # f[a-h] partition fragment sizes in bytes # d[a-h] partition density (bytes-per-inode) # r[a-h] partition minfree # # [da -> 1 inode per 8k disk data space (quite generous, actually)] # [..... with a full disk, we only use 17% of inodes] # [ra -> reserve 10% disk space] omd-1|OMD-1|Canon OMD-1:\ :ty=removable_rw_optical:nc#1029:nt#15:ns#16:ss#1024:rm#3000:\ :fp#256:bp#256:ng#153:gs#1600:ga#16:ao#784:\ :os=odmach:z0#80:z1#168:ro=a:\ :pa#0:sa#242352:ba#8192:fa#1024:ca#6:da#8192:ra#10:oa=time:\ :ia:ta=4.3BSD:aa: # # One model of the 330M disk used 512 byte sectors. -------------------- Brad Carlson <carlson@mrcnext.cso.uiuc.edu> or <b-carlson@uiuc.edu> University of Illinos--Micro Resource Center--NeXT guru