 The Safety Space Manager as HSM   H Note that Safety shelving and unshelving normally uses a pair of commandF files to accomplish its work...these are ultimately renamed filsav andI filrst...but a number of file pairs named JTFILSAV*.com and JTFILRST*.com F are present in the kit. You may prefer to use something other than theJ default pair. The default pair will store files in one directory somewhereE and retrieve from there (with optional compress/decompress),but this  E area can fill. The *mdir* versions supplied use file ID to spread the A stored files over many directories. Note too that a Safety server @ can shelve files from disks it handles to somewhere else. If youC have more than one Safety server, it is possible to have one server G shelve files to a nearline store, and have a second server handling the A nearline store notice that this is filling up and shelve files to H a less-nearline store, in as many steps as you like. Some of the command) files are starts at doing backup to tape.   F Note that all files get stored or restored using normal VMS utilities,F and the filenames used for storing the files are composed of the firstC part of the original filename plus the file ID. Since a "stub" will D be left with the original file ID, the shelving operation can alwaysC be reversed manually, even if Safety isn't present to do it. A menu H option does however exist in jt_setup.com to let you unshelve everything provided there's room enough.   D Files are shelved using normal copy or backup, the optional compressD done using zip (which can be undone on many different system types),E and can be accessed transparently. Note too that if you choose to use B the "softlink" capabilities, Safety can be used to allow access toA "shelved" files directly from the shelved area. However, in doing C this, note the files must be shelved non-compressed. If you want to D store them compressed, buy Acorn Squash (a compressing virtual disk)E or perhaps the Montagar compressing package, and use that in the .com D files. You can edit filsav.com and filrst.com yourself, but rememberD that what filsav.com shelves, filrst.com must unshelve, and must notF mess up files. The filrst.com procedure runs BEFORE the file is openedC by the user; Safety catches the open request before it hits the VMS  file system.  A The following describes the use of Safety as an HSM package. Just A remember the cautions above. The menus are not tailored in detail > for simplest use of Safety in an HSM capacity but the MOVEFILED command is defined at Safety login to let you select a file or filesA to shelve (and how to shelve them), and there is a site script to B set shelving policy. This script is menu driven and fairly obvious to use.              Description:  K           Safety(HSM) is an add-in to the VMS I/O system which provides VMS K with the ability to have transparent file migration between active and near K line storage in one or more steps. When files are migrated ("shelved") from J normal disk storage to backing storage, a marking is left on them which isG automatically read so that when the file is opened, it is automatically G retrieved by Safety(HSM) from nearline storage. Thus, a user or program D need not be aware at all that such shelving occurred and no operatorF intervention is needed to perform the "unshelving" operation.  This isH distinguished from operation where a user must first request an archivedJ file be reloaded, which requires detailed advance knowledge of such needs.J The files appear to have been on disk all the time, but in fact the onlineJ disk space is conserved. It is also distinct from modes of operation whereG a file's location visibly changes. These, too, require that programs be G told where the new site is, which can be awkward.  Safety(HSM) provides K total transparency of file migration, invisible to programs and users apart H from small delays where files must be unshelved. Shelving and unshelvingE can be controlled by scripts which can place files even on sequential C devices like tape, or store files in compressed form, decompressing ( automatically when the file is accessed.  B           In addition, Safety(HSM) provides two unique "soft link"@ abilities which complement unshelving, and manages volume space.  :           The basic capabilities of Safety(HSM) are these:  K           * Files can be shelved (by space-making script or by command) and G unshelved automatically from nearline storage when they are opened. The K process opening the files then sees a successful open with no side effects. J Shelved files can be stored in compressed form if this is desired, and canH be stored in any desired location.  Storage of shelved files on tapes or the like can be done also.  I           * Files can be "soft linked" to other files, even across disks. K This mode of access can be used for a sort of permanent shelving on another D volume by truncating the original file to zero blocks. The soft linkK operates extremely fast and causes the file in question to be opened in its H new location, with the channel restored on close so that again a programK observes no change, but the file is accessed transparently at its new site. I Where the new site is a read/write device this can be most effective. The K file appears to be at its old location, but in fact resides somewhere else.   F           * Files can be "soft linked" in a "readonly" mode to anotherK file. In this mode, suitable for read-only backing storage, whenever a file K is opened for read-only access, it is transparently and instantly opened on G its linked site, wherever that may be on nearline storage.  When such a K file is opened for any kind of writing, however, it is treated as a shelved J file and is unshelved and replaced on normal disk before the open is done.H Thus any read/write access will find the file in a suitable location forJ its open to succeed, transparently.  (Notice that soft linked storage mustG be on disks and must not be in compressed form. The decompression would $ induce an unwanted delay in access.)  G           * Disk space can be managed. Whenever an extend or create (or C inswap) would not have adequate space on disk, Safety(HSM) starts a K "make-space" script which is tailored by a fullscreen utility to match site J policy.  This policy can select files based on access time, size, name, orJ characteristics for space making. A utility is provided to simplify policyF selection. The "make space" script can be run at any time (e.g. in the  middle of the night) if desired.  K           Safety(HSM) tailoring can be done either for the entire system or K for any number of disks at a time. Thus it is possible to have a multi-tier K migration strategy with each tier managed by a separate Safety(HSM) server, H so that files may migrate toward slower storage but still be retrievableF transparently no matter how far down the hierarchy they have migrated.J Features of Safety(HSM) can be separately enabled or disabled as well on a( per server basis should this be desired.  K           File migration can also be handled by a simple command which runs H a menu driven selection of how the file is to migrate and in which mode.H Provision exists to regenerate file markings in case they are lost or toK audit the markings. Also, it is possible to specify exempt images which are I not subject to file unshelving, or to set a process temporarily as exempt I from unshelving or softlinks, so that operations which must view the disk 0 without triggering unshelving can be easily run.  H           Safety(HSM) can be run in a mode where there is essentially noK overhead at all imposed (just a few instructions added along some paths and K no disk access) for any files except those which need softlinks or possible K unshelving. There is no limit to how many files may be so marked on a disk. I A fullscreen setup script allows one to select the Safety(HSM) run modes. H Even if Safety(HSM) is forced to examine all files for its markings, theF overhead imposes no added disk access and costs only a tiny added timeI (typically a percent or two) in open intensive applications. In addition,eG Safety(HSM) can be turned off or back on at any convenient point shoulda this be desired.             Support:  D           Safety(HSM) runs on VAX VMS 5.5 or greater, AXP VMS 6.1 orK greater. The same facilities exist across all systems.  Safety(HSM) must benI installed on each cluster node of a VMScluster where it is to be used but G imposes no restrictions on types of disk it works for. Safety(HSM) willoK work with any file structure used by VMS, so long as a disk class device isdH used to hold it. It is specifically NOT limited to use with ODS-2 disks.I Where Safety(HSM) is run on only some nodes of a VMScluster, its featureshE will not be usable on the other nodes, but no ill effects will occur.i     General Cybernetic Engineering 18 Colburn Laner Hollis, NH 03049 603 465 9517   Glenn C. Everharte Everhart@GCE.Com