Hi all , Got replies from Russell Page and Andrew Hay . Thanks a lot guys . certainly made things a lot clearer . The parameter can be set using newfs as Andrew pointed out . Should have gone through the man pages more carefully . Andrew said : "From: accy guy <accy_guy@yahoo.com> " "Can anyone provide me pointers as to what frag size parameter is as shown in df -g for most accesses, a largeish block size is more efficient considering all the time spent seeking, but to more efficiently handle small files a fragment of a block can be allocated. why not just have smaller blocks? i don't know. i also don't know why disks are still formatted with tiny sectors when all transactions are in multi-sector groups. "sys1# df -g /var/crash " "/var/crash (/dev/vx/dsk/usrdg/crash): 8192 block size 1024 frag size " 6291456 total blocks 6028340 free blocks 5651580 available 753552 t "otal files " 753542 free files 35656586 filesys id " vxfs fstype 0x00000004 flag 255 filename length " " "Can this parameter be set ? 2 different solaris 8 systems with Vxfs filesystems show different values of frag size ... One shows 1024 and the other shows 8192 . it can, at newfs time. Russell said : Solaris (and most other UNIX systems) use a file system specifically developed to optimize disk storage and minimize file fragmentation. Typically the system works with "blocks". On Solaris a block is usually 8k in size. However 8k is a very inefficient size to allocate to small files. Say you have fifty files with an average size of say 700 bytes, you end up allocating 400k to store 35k of data. To get around this problem, each block is divided into 8 fragments. The block is still the smallest unit read or written by the kernel, but the smallest unit that can be allocated to a file is 1 fragment. In my example, each 700 byte file occupies 1 fragment, and the kernel can store 8 files in one block. So we end up allocating 7 blocks to store our 50 files. Our 35k is now packed into 56 k of storage. Generally, the kernel will a pack file into the minimum number of blocks and fragments it can fit into. The file layout is maintained dynamically, so generally UNIX file systems don't become fragmented in the way that Windows one do. However the kernel needs a pool of free space to do this. Usually, we give the kernel a 10% margin to play with. This is the reason why df will tell you the filesystems are 100% full when they are actually only 90%. The UNIX file system is a very elegant piece of software. The BSD documentation has a nice article about it. You can download a copy from here: ftp://ftp.netbsd.org/pub/NetBSD/misc/lite2-docs/smm/05.fastfs.ps.gz Hope this makes sense. Thanks once again Accy accy guy <accy_guy@yahoo.com> wrote: hi admins , Can anyone provide me pointers as to what frag size parameter is as shown in df -g sys1# df -g /var/crash /var/crash (/dev/vx/dsk/usrdg/crash): 8192 block size 1024 frag size 6291456 total blocks 6028340 free blocks 5651580 available 753552 t otal files 753542 free files 35656586 filesys id vxfs fstype 0x00000004 flag 255 filename length Can this parameter be set ? 2 different solaris 8 systems with Vxfs filesystems show different values of frag size ... One shows 1024 and the other shows 8192 . Thanks & Regards Accy The New Yahoo! Shopping - with improved product search _______________________________________________ The New Yahoo! Shopping - with improved product search _______________________________________________ sunmanagers mailing list sunmanagers@sunmanagers.org http://www.sunmanagers.org/mailman/listinfo/sunmanagersReceived on Wed Oct 8 07:07:40 2003
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