NetNews Usenet Archive 1992 #16

home *** CD-ROM | disk | FTP | other *** search

/ NetNews Usenet Archive 1992 #16 / NN_1992_16.iso / spool / comp / sys / ibm / pc / misc / 10919 < prev next >

Wrap

Internet Message Format | 1992-07-28 | 16.5 KB

Path: sparky!uunet!centerline!noc.near.net!hri.com!ukma!darwin.sura.net!mips!sdd.hp.com!hpscdc!hplextra!hpcc05!hpbbn!hpuamsa!franks From: franks@hpuamsa.neth.hp.com (Frank Slootweg CRC) Newsgroups: comp.sys.ibm.pc.misc Subject: Re: Re: Need Advice on Hard Disk Backup Systems Message-ID: <26790015@hpuamsa.neth.hp.com> Date: 27 Jul 92 13:47:30 GMT References: <4795@unixhub.SLAC.Stanford.EDU> Organization: Hewlett-Packard, The Netherlands Lines: 308 esr@unixhub.SLAC.Stanford.EDU (Edwin S. Russell) writes: > As I noted a few months ago in a similar post, I stopped using PCBackup > because of its intermittent problems with being able to restore. Backup > works great but several people have reported problems restoring. The third > time I couldn't restore files I scrapped it. I now use Fastback. The original poster and other netters may benefit from a repost (if this, rather lengthy, repost violates some Netiquette, then please educate me) : From franks Tue Jul 7 08:45:03 1992 From: franks@hpuamsa.neth.hp.com (Frank Slootweg CRC) Date: Tue, 7 Jul 1992 06:45:03 GMT Date-Received: Tue, 7 Jul 1992 06:45:03 GMT Subject: PC Tools 6.0 PCBACKUP Restore tips. Message-ID: <27210008@hpuamsa.neth.hp.com> Organization: HP-Sales Office-The Netherlands Path: hpuamsa!franks Newsgroups: comp.os.msdos.apps PC Tools 6.0 PCBACKUP Restore problems and solutions/workarounds. ================================================================= Note: I originally wrote this article as an e-mail message to someone. In order not to have to rewrite it, I just deleted the recipients' name and other personal or irrelevant information. Hello [deleted], I did some restore experiments with PCBACKUP from PC Tools 6.0. Bottom line: I have not been able to completely reproduce your scenario ("Try restoring with diskette 1 and it claims foul. Try restoring with diskette 2 (with the "log") and it complains that it can't find diskette 1."). I have, I think, been able to reproduce the first part of this scenario. Details follow later. HOWEVER I have, intermittently, had files which were TOTALLY CORRUPTED (wrong size and totally wrong contents) after a restore which gave NO ERRORS whatsoever. This scenario is at least as bad, or even worse, as yours. I say "intermittently" because sometimes the restore is OK and sometimes it is not. I have not been able to accurately pinpoint under which circumstances the restore fails, but I have been able to find a scenario which "never" fails (worked OK at least 10 times). Since I wanted to go as far "to the bottom of it" as I could, I documented my experiments in rather much detail. If there is sufficient interest in some comp.os.msdos.* or comp.ibm.pc.* group, then I will post this information or a summary of it. If you do not want to read it all, then you might still be interested in my main conclusions : - Your "Try restoring with diskette 1 and it claims foul." scenario was perhaps caused by a combination of operator error and the illogical and (probably) inconsequent user interface of PCBACKUP. - Under as yet unclear circumstances the content of files restored by PCBACKUP can be corrupt without any error or warning. The corruption occured several times when the Super PC-Kwik disk cache was enabled. It did not occur when the cache was disabled. However later tests with cache enabled gave no corruptions, so it is unclear if the disk cache, PCBACKUP or something else was causing the corruption. Another ([deleted]) user also had corrupt restored files. He will try if he can reproduce his failure scenario. If so, he will inform me and I will inform you. [deleted] Before I describe the details of my tests : I think I was able to reproduce the first part of your scenario ("Try restoring with diskette 1 and it claims foul."). Details of attempts to reproduce the first part of your problem =============================================================== 1. If, when PCBACKUP wants to read the directory information ("log"), you insert the wrong disk, i.e. any disk other than the last one, then PCBACKUP gives a dialog box '!ERROR! Backup Directory Not Found. Choose "Retry" if wrong disk inserted. Choose "Rebuild" to regenerate directory from backup set.'. At this moment one should insert the last disk and, with the "Retry" button highlighted, press the "Return" key (which "presses" the highlighted button). Note: In medium or high speed mode, but not in low speed mode, this is different than for the "Insert last disk in drive B:" dialog box described in point 4 below : - For the "Insert ..." dialog box PCBACKUP will automatically continue when a disk is inserted (provided the diskette drive has volume-change detection hardware, which all somewhat modern drives do have). Once the disk is inserted the "Tab" key (to switch between the buttons) and the "Return" key (to "press" the highlighted button) have no effect. - For the "!ERROR! ..." dialog box one *must* press the "Return" key in order to "press" the highlighted "Retry" button. If one does not press "Return" then the following very strange scenario can occur : - After, in my case, 1.45 minutes the access light of the diskette drive goes off. - Smart user remembers that (s)he should press "Return". - After "Return" is pressed the "Insert last disk in drive B:" dialog box appears, but, while the correct diskette is in the drive the light remains off. - Smart user again presses "Return" for the highlighted "OK" button, but the access light remains off. - Smart user is patient and waits. After, in my case, ~24 seconds the access light goes on and after another ~27 seconds the "Reading Directory Information Please wait." information box is shortly shown and all is well again. So to summarize this point(all for medium or high speed mode): For the "Insert ..." dialog box one *can not* (as in: has no effect) press the "Return" key to press the highlighted "OK" button. For the "!ERROR! ..." dialog box one *must* press the "Return" key to press the highlighted "Retry" button. See also recommendation 7 below for another scenario which may make you think that your backup set is bad while it actually is perfectly OK. Details of my own problems ========================== 2. I do not think that my problems had anything to do with the "log" files. When requested PCBACKUP makes an ASCII DYYMMDDA.RPT file and a binary DYYMMDDA.DIR file on the harddisk (D=drive, YY=year, MM=month, DD=day_of_the_month). Only the .DIR file is used during the restore, i.e. if it is available then the directory information is read from it, else you have to select the "Insert" button of the "cHoose directories" sub-menu "to read the directory from an inserted Disk". 3. Just to really emulate a restore to a clean/empty disk, I copied my *.SET, *.RPT, *.DIR, PCBACKUP.HST and PCBACKUP.CFG files to a diskette and then removed them from my harddisk. 4. One point which is very confusing and which probably creates problems for a lot of users is the following (again for medium and high speed mode) : When selecting the "Insert" button from the "cHoose directories" sub-menu to read the directory from the last disk of the backup set, one shortly - a few seconds - gets a information box saying "Reading Directory Information Please wait." and then a dialog box "Insert last disk in drive B:" with "OK" and "Cancel" buttons. The drive access light goes on and the drive is ready to accept the diskette. So far, so good. Now you insert the last diskette. For my 3.5 inch B drive you just hear some clicking, i.e. the latch of the diskette is opened, and then nothing *seems* to happen for about 1.5 minutes (I had a set of 9 diskettes). Even the "Insert last disk in drive B:" dialog box is still there and its "OK" button is still highlighted. *IF* you are smart enough not to touch anything and just patiently wait, then *AFTER* the 1.5 minute period you shortly - a few seconds - get an information box saying "Reading Directory Information Please wait." (and, even shorter, another information box saying "Reprocessing selection list. Please wait."). After that, as expected, the directory structure from the backup set is shown (two boxes, directories on the left, files on the right). This way of operation is very confusing. Because nothing seems to happen, users are probably going to press keys, remove and re-insert diskettes, etc. Of course the "Insert ..." dialog box should disappear as soon as the diskette is inserted and the "Reading ..." information box should be shown during the 1.5 minute wait. Note: If the last diskette is put in the drive *before* PCBACKUP says "Insert last disk in drive B:", then PCBACKUP directly reads the directory information, i.e. no 1.5 minute wait. 5. I think my problem (PCBACKUP gives no error messages, but restored file is totally corrupt) is caused by PCBACKUP reading the file content from the wrong diskette. I restored only one directory with two files. One of the files was also on the harddisk and I did not let PCBACKUP overwrite this file. The directory ("log") was on the 9th diskette and the files to be restored were on the 1st diskette. I did the following tests, most of them multiple times : - Insert last diskette when PCBACKUP instructs you to do so, select directory to restore, *leave* last diskette in drive, select "Start restore" and insert diskette 1 when PCBACKUP instructs you to do so. Result: Restored file sometimes OK, sometimes corrupt. - Insert last diskette when PCBACKUP instructs you to do so, select directory to restore, *remove* last diskette from drive, select "Start restore" and insert diskette 1 when PCBACKUP instructs you to do so. Result: Restored file *always* OK. - Disabled cache. I use DR DOS 6.0 and its bundled Super PC-Kwik cache. Super PC-Kwik can also cach diskette reads and I have enabled this feature. For people "in the know" : I also use the /V+ switch ("Use volume change hardware.) and the volume change hardware tests as described in the DR DOS 6.0 manual work correctly on my system. Rest as first scenario : Insert last diskette when PCBACKUP instructs you to do so, select directory to restore, *leave* last diskette in drive, select "Start restore" and insert diskette 1 when PCBACKUP instructs you to do so. Result: Restored file *always* (10 times in a row) OK. - Happened only once: Disabled cache. Insert last diskette when PCBACKUP instructs you to do so, select directory to restore, *leave* last diskette in drive, select "Start restore". PCBACKUP did *not* ask to insert diskette 1, read from the last diskette, said "Restore Completed!", but the restored file was (of course) totally corrupt. So I think that, unless the right diskette is in the drive when PCBACKUP starts reading the file contents, PCBACKUP sometimes reads the wrong file contents. How it can read the wrong contents when it does ask for the right diskette, the right diskette is inserted and PCBACKUP seems (since the drive access light is on before the diskette is inserted, and my 3.5 inch drive is very quiet, it is hard to tell if the drive is actually reading) to read the right diskette, is beyond me. Perhaps it is caused by the cache and is the "Happened only once:" problem caused by the drive thinking that a new diskette was inserted (i.e. failing volume-change detection hardware in the drive). Another observation: If the restore from the requested diskette is fast - a few seconds for this one 1565 byte file - then the restored file is OK. If the restore is slow, some 15 seconds, then the restored file is corrupted. The bad news : After the above experiments I retried the first scenario (which earlier sometimes gave a corrupted file). However this time I never got a corrupted file, even not after over 20 tries! So I could not reproduce the problem scenario again and therefore can not determine what caused or may have caused the corruption. Based on the above and other experience, I have the following recommendations : 1. Do not use a disk-cache when restoring a PCBACKUP backup. It is probably also wise to not use a disk-cache when making the backup, but if you specify "Verify Always" (only checks if the backup can be *read*, does *not* do a *compare*, see manual) before the backup and do a compare ("start Compare") after the backup, then, if the compare is successful, your backup should be OK. 2. For medium or high speed mode : If you know that you have inserted the *right* diskette after PCBACKUP instructed you to do so, and nothing *seems* to happen, i.e. the previous dialog box is still shown and the selected button is still highlighted, then please be patient, do not press any keys, do not use your mouse (if available and installed), do not remove the diskette and wait at least a few minutes to see if PCBACKUP actually *did* do something and continues (i.e. screen content changes). During the wait time the disk access light should be on. If it is off then press the "Return" key while the desired button is highlighted. If the desired button is not highlighted, then try if you can highlight it by pressing the "Tab" key. After each action wait at least again a few minutes before giving up. See also 6. 3. Remove the last diskette directly after the directory information has been read ("Reading Directory Information Please wait"). Do *not* wait untill PCBACKUP instructs you to insert another disk. 4. Remove a diskette directly after PCBACKUP stops reading it. Do *not* wait untill PCBACKUP instructs you to insert another disk. I.e. similar recommendation as for the last diskette, but now for any diskette (including the last). 5. Do not insert a diskette untill PCBACKUP instructs you to do so. Exception: Insert the last diskette before PCBACKUP instructs you to do so, i.e. for "Insert" button of "cHoose directories" sub-menu or for "Start restore" sub-menu when doing a full restore (i.e. "cHoose directories" was not used earlier). 6. When PCBACKUP instructs you to insert a disk then do not insert another disk than the one which PCBACKUP requests. If you have not yet labelled your disks with the right numbers, or have incorrectly labelled them, then do a DIR for each of the disks. The DIR output will show PCBACKUP.001 for disk 1, PCBACKUP.002 for disk 2 and so on. The PCBDIR program will give similar, and more, information. If you, by accident, insert a wrong disk then remember the following : - For the "Insert ..." dialog box PCBACKUP will automatically continue when a disk is inserted (provided that PCBACKUP is configured for medium or high speed mode and the diskette drive has volume-change detection hardware, which all somewhat modern drives do have). - For the "!ERROR! ..." dialog box you *must* press the "Return" key in order to "press" the highlighted button (in most cases the "Retry" button). - If you get "hung" for more than a few minutes while the "Insert ..." or "!ERROR! ..." dialog box is displayed, then it is probably best to start over (i.e. try to stop PCBACKUP and if that fails reboot with Ctrl-Alt-Delete). Do *not* conclude that your backup is bad if you get "hung" while the "!ERROR! ..." dialog box is displayed. Most likely your backup and the PCBACKUP program are OK and just your multiple errors caused a (real or apparent) hang condition. 7. A backup set made in low speed mode must be restored in low speed mode. A backup set made in medium or high speed mode can be restored in medium or high speed mode. If you have configured the wrong speed, then PCBACKUP will give the "!ERROR! ..." dialog box, even if your backup set is OK and you have inserted the correct (last) diskette. The /X option of PCBDIR will tell with which speed a particular backup set was made. It will say "high" for both a medium and high speed backup set. The purpose of recommendations 3, 4 and 5 is to make sure that the right diskette is inserted at the moment when PCBACKUP needs it and a diskette is removed as soon as PCBACKUP is finished with it. This hopefully prevents PCBACKUP from (trying to) read(ing) the wrong diskette. I hope (at least some of) this is of use to you. Best regards, Frank Slootweg, UNIX support person and PC owner.