D FRAGAVOID, System_Management, a tool to prevent disk defragmentation  H Fragmentn Avoid, DEFRAG, Avoid ~98% of dsk frag, 30%+ Disk Speedup w/srcK Released by Acorn and GCE for the freeware CD or other general consumption.        	The Fragmentation Avoider  F This utility actively prevents most disk fragmentation from occurring,F so that disks run less fragmented, and usually considerably faster. ItH can be set up and left running with no attention; you configure it, turnH it on, and forget it, enjoying faster I/O and disks that grow fragmentedI much more slowly than before. Your access to disks does not change at all 
 in detail.  F This utility for Vax or Alpha came out of the Safety product availableF from General Cybernetic Engineering and was extended by Acorn SoftwareF to make its user interface more usable. It is presented in source as a@ "calling card"; we hope that you will look over the SPDs for theG Acorn products and for the Safety components DPS and EACF in this area. B They provide many services for storage management unavailable fromH any other places and include a complete "operator in a box" solution forK tape jukeboxes, a cluster-aware disk jukebox solution that allows failover, E and does not exhaust the MSCP server, full function, multi-level HSM, I realtime compressing storage (disk space trebler), reliable user UNDELETE M (which turns deletion to a "move to wastebasket"), and vast extensions to VMS  file security.   Now to the Frag Avoider.  D The frag avoider will largely prevent disks from becoming fragmentedG and will speed up disk access. In a nutshell, FA causes file extends to C be a fraction of the initial file size (with some safeguards so the H disk isn't filled etc.) so that VMS will not need to extend it as often.C This results in files less fragmented than they otherwise would be, D and writing doesn't need to "go to the well" as often. Some tests ofF random loads have shown up to a 30% speedup. (Enjoy!!) It also by thisB means, and by doing extends Contig Best Try, reduces the amount ofG "chaff" space in the extent cache, so your files tend to be placed with F a "first fit" algorithm. The reduced fragmentation speeds read access.G It will not interfere with normal operation or even disk defragmenters, I but if you are nervous it can be turned off or on when you want. Normally A it is expected to be set up in your systartup_vms script however.   9 FA has been in use at several sites for a few years now.    @ VMS disks in ordinary operation become fragmented rather quicklyD once defragmented. This leads to files which require many index file? reads to locate and to lots of unnecessary disk head motion. On G optical disks, this is an even worse problem, since seek times are much  longer than magnetic disks.   > There are several reasons for this rapid refragmentation whichB deserve exploration. First is the way VMS uses its "extent cache".B Whenever disk space is released, pointers to it are kept in memoryC awhile, so that space can be quickly allocated. The problem is that A whenever files are closed, they are generally truncated to return B extra allocated space to the system. The returned space is usuallyD in small pieces, and thus new space requests wind up being satisfiedD from the last bunch of these little pieces of disk, rather than fromD larger areas. When files are deleted, they leave these pieces aroundH which only get cut up still more with time. The result is fragmentation.  C Also, it is often the case that files are left open for fairly long @ times, and grow a few blocks at a time, typically allocating theA volume default allocation, but sometimes allocating a small fixed > number of blocks. Many of these files may grab 5-block extentsC thousands of times over their lives; this inevitably produces badly C fragmented files which are hard to defragment because they're open. B It also wastes a lot of time calling the file system for every few blocks.   B The Fragmentation Avoider is a system for automatically addressing6 these problems, and incidentally solving a few others.  @ The Fragmentation Avoider arranges for file extension to be done? "Contiguous Best Try" when this is possible. This causes VMS to ? flush (i.e., forget about) its extent cache and attempt to find @ a space big enough to hold the whole requested area before usingC badly fragmented store. The program can do this for every extension > (the default and recommended behavior) or every Nth extension,? if you feel the need to have the extent cache used, but cleared  periodically.   A Fragmentation Avoider also controls the amount of space requested = when a program extends a file (i.e., makes it longer). It can ? set a minimum extent request, so even explicit requests for one ? block at a time can be increased, and is able to request that a B file be extended by 1/N of its current size, subject to free space> constraints on the volume and a maximum extend amount. It will@ always request at least as much space as the program wanted, butD will attempt to extend by 1/N of the file size, 1/8 of the available@ free space on the disk, or the maximum extent request, whichever	 is least.   D File extension is an expensive operation; by arranging it to be less? often needed, F.A. can permit file writing to enjoy up to a 30% I speed gain, in addition to permitting faster access to files written with ? it. This is the gain from not having to do the extend operation 	 as often.    SUMMARY:  A Fragmentation Avoider permits disk fragmentation to be controlled ; by altering somewhat the VMS file extend operation in a way A that greatly slows the refragmentation of disk space. The package ; can be installed on any disks where this is desired and its ; parameters can be set on a per-disk basis. Disks where the  6 Fragmentation Avoider is not installed are unaffected.    
 Installation:   6 See the AAAREADME.TXT. FA is installed with VMSINSTAL.  & (And don't forget to read the SPDs!!!)  