From: Christian.Andretzky@TU-Chemnitz.DE (Christian Andretzky)
Subject: Re: any advice on Seagate hard disks with a NeXT?
Reply-To: Christian.Andretzky@TU-Chemnitz.DE
Organization: University of Technology Chemnitz, FRG
Date: Fri, 22 Jan 1993 14:07:02 GMT

In article <C18twp.4Is@ccu.umanitoba.ca> tilley@ccu.umanitoba.ca (Richard  
Tilley) writes:
> In <1993Jan20.144630.16352@mb3.tu-chemnitz.de>  
Christian.Andretzky@TU-Chemnitz.DE (Christian Andretzky) writes:
> 
> 
> >In general reformatting a disk from the default sector size (512) to 1024  
> >B/sector will increase the available raw disk space to appr. 105% of the 512  
> >capacity.
> 
> >For example in my cube is a seagate st42400n which has a raw capacity of
> >203x MB (512B/sec) and a formatted capacity (df)
> 
> >/dev/sd1a         1729424  474633 1081848    30%    /disk1
> 
> >after reformatting the drive to 1024 the raw capacity is 2175 MB and the
> >formatted capacity (df) is now
> 
> >                      2138695
> 
> This looks like 24%.
> The raw increase looks like 7%.
> Did you reduce the number of spare sectors to get that 24%?
I did nothing special - I used disk to define the partition(s)
Note: for maximum storage capacity the size of the first partition should be a  
multiple of 7 MB (because the minimal size of a cylinder group which can be  
defined via newfs/mkfs is 7 MB)
Then I used newfs with the parameters -c 8 and -r 5400 all other parameters  
were default values (r 5400 because the disk has indeed 5400 rpm, c 8 because  
mkfs gives the hint to reduce the number of cylinders per group to reduce the  
number of bytes per inode)
The value of 8 for Cyl. per group is sure not the optimum but ther is a bug in  
mkfs - the man pages say possible values for c are between 1 and 32 but mkfs  
self accepts only values which are multiples of 8 (This reduces the number of  
possible values drastically if the default value which should be changed is 16  
;-)
Here FYI a dump from newfs/mkfs:

steve:5# newfs -N -v -c 8 -r 5400 /dev/sd1a
setting optimization for space with minfree less than 10
/etc/mkfs -N /dev/rsd1a 1612951 45 19 8192 1024 8 0 90 2048 s
Warning: 2048 bytes per inode impossible due
to cylinder group size, using 2393 bytes per inode
Reduce cylinder group size to reduce bytes per inode.
Warning: 434 sector(s) in last cylinder unallocated
/dev/rsd1a:     1612951 sectors in 1887 cylinders of 19 tracks, 45 sectors
        1651.7Mb in 236 cyl groups (8 c/g, 7.00Mb/g, 2048 i/g)
super-block backups (for fsck -b#) at:
 16, 6904, 13792, 20680, 27568, 34456, 41344, 48232, 55120, 62008,
 68896, 75784, 82672, 89560, 96448, 103336, 110224, 117112, 124000, 130888,
 137776, 144664, 151552, 158440, 165328, 172216, 179104, 185992, 192880,  
199768,
 206656, 213544, 218896, 225784, 232672, 239560, 246448, 253336, 260224,  
267112,
 274000, 280888, 287776, 294664, 301552, 308440, 315328, 322216, 329104,  
335992,
 342880, 349768, 356656, 363544, 370432, 377320, 384208, 391096, 397984,  
404872,
 411760, 418648, 425536, 432424, 437776, 444664, 451552, 458440, 465328,  
472216,
 479104, 485992, 492880, 499768, 506656, 513544, 520432, 527320, 534208,  
541096,
 547984, 554872, 561760, 568648, 575536, 582424, 589312, 596200, 603088,  
609976,
 616864, 623752, 630640, 637528, 644416, 651304, 656656, 663544, 670432,  
677320,
 684208, 691096, 697984, 704872, 711760, 718648, 725536, 732424, 739312,  
746200,
 753088, 759976, 766864, 773752, 780640, 787528, 794416, 801304, 808192,  
815080,
 821968, 828856, 835744, 842632, 849520, 856408, 863296, 870184, 875536,  
882424,
 889312, 896200, 903088, 909976, 916864, 923752, 930640, 937528, 944416,  
951304,
 958192, 965080, 971968, 978856, 985744, 992632, 999520, 1006408, 1013296,  
1020184,
 1027072, 1033960, 1040848, 1047736, 1054624, 1061512, 1068400, 1075288,  
1082176, 1089064,
 1094416, 1101304, 1108192, 1115080, 1121968, 1128856, 1135744, 1142632,  
1149520, 1156408,
 1163296, 1170184, 1177072, 1183960, 1190848, 1197736, 1204624, 1211512,  
1218400, 1225288,
 1232176, 1239064, 1245952, 1252840, 1259728, 1266616, 1273504, 1280392,  
1287280, 1294168,
 1301056, 1307944, 1313296, 1320184, 1327072, 1333960, 1340848, 1347736,  
1354624, 1361512,
 1368400, 1375288, 1382176, 1389064, 1395952, 1402840, 1409728, 1416616,  
1423504, 1430392,
 1437280, 1444168, 1451056, 1457944, 1464832, 1471720, 1478608, 1485496,  
1492384, 1499272,
 1506160, 1513048, 1519936, 1526824, 1532176, 1539064, 1545952, 1552840,  
1559728, 1566616,
 1573504, 1580392, 1587280, 1594168, 1601056, 1607944,
steve:6# 

As you can see the number of cyl. per group should less than 8. No matter which  
walue is entered for bytes per inode, the warning is displayed each time. (If I  
enter 2393 too)

HTH, Christian
--
Name:  Christian Andretzky      | Address: Technische Universitaet Chemnitz |
Phone: +49 371 561 2130         |          Fachbereich Maschinenbau III     |
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mail: Christian.Andretzky@TU-Chemnitz.DE   D-O-9022 Chemnitz                |
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