Report on long-term use of multisession DVD+R

[Flash]

On 24 May I burned Puppy2 alpha (24 May snapshot) on a multisession DVD+R. So far I have saved 103 sessions to this disk, not counting the original files from the iso, which must also count toward the mythical 100-session limit of a DVD+R. I have read that the power calibration area of the DVD+R was designed with only enough room for 100 power calibrations. Perhaps the burning program can ignore this limit if the drive can find room in the power calibration area for one more go.

When I booted just now, it took 2 minutes 15 seconds from the time I pushed the start button until Puppy barked. Almost 30 seconds went by after the button was pushed before the DVD drive actually began to read the disk, so it really only took 1 minute 45 seconds to boot this Puppy. My DVD drive is a Memorex that I believe reads the disk at 16x.

According to my ruler, of the 1.44 inches of usable radius of the disk, 1.25 inches has been burned. ROX's "disk usage" reports 2820 Mb used, but from its appearance I'd say more of the disk's 4.7 GB capacity has been used than that.

There was one instance when Puppy refused to save a session at shutdown. When that happened it wouldn't let me back out of the shutdown window; all I could do was force a shutdown and lose the session. Since then, if it is important to save a session, I use the "Save" icon on the desktop because it looks like I can kill the savesession program from its dialog window if it doesn't work. I haven't actually tested it to see if I can. I wish I knew why it wouldn't save, that one time. Was it something I did?

The biggest file I saved to this DVD was MU's 200 MB Megapup. I downloaded it straight to the Archive, so that it would be saved when I shut down but not reloaded into RAM when I restarted. I've also downloaded Puppy2.0.1 to the archive and a few other things, to have them handy for making my next multisession DVD. Since Puppy does not keep an index of the Archive contents, I used Gnumeric to create a spreadsheet where can keep a record of the items I put in the Archive, along with the ID of the session where that Archive can be found.

[marksouth2000]

According to my ruler, of the 1.44 inches of usable radius of the disk, 1.25 inches has been burned. ROX's "disk usage" reports 2820 Mb used, but from its appearance I'd say more of the disk's 4.7 GB capacity has been used than that.

Remember that the data storage used is not a linear function of the radius burned. The outer part of the disc holds more data per circuit than the inner. That last quarter-inch holds roughly twice as much as the innermost quarter-inch.

[raffy]

one instance when Puppy refused to save a session at shutdown. When that happened it wouldn't let me back out of the shutdown window

Maybe you could try CTRL-C, which will bring up the console, and then "poweroff" while at the console. That worked for me once. At least you could use a different disc if it really wont save, or save to other media by starting "xwin".

[3133]

I can't reconcile my experience of the multisession DVD with that described by Flash.

Running Puppy 2.01 on DVD-R, 512 Mb memory, no hard drive, machine dedicated to Puppy. After 13 sessions was asked to insert blank disc to save the 14th session. This surprised me. The only save of any note on the 13 sessions was one file of approx 70 Mb. Followed instructions to the letter, but new DVD was not burned.

Decided to start again from scratch. Attempted to download Puppy 2.01. No joy. Not enough space. Little blue window showed 123Mb free out of my 512. Opened console. 'df -h' said I had around 250 Mb available. Who to believe? OK, I had the ISO on another machine and could transfer it via a memory stick to the Puppy machine (the only one with a DVD burner) and maybe get the job done that way, but I don't understand why this should be necessary, any more than I understand why I was able to save only 13 sessions containing an insignificant amount of data.

Any advice or comments from more informed members of the Puppy community would be heartily welcomed.

3133

[raffy]

One guess - large files should be put in /root/archive so that they are not inserted to memory at boot-up and therefore not consume memory. They can still be read by mounting the DVD (with Mut).

DVD-R's are prescribed. Some problems are noted with other types of DVD media.

Edit for Flash, from http://puppyos.com/multi-puppy.htm : "I strongly recommend that you use a single-layer DVD-R. Do not use a DVD+R, DVD-RW or DVD+RW, as each of these seems to have particular problems."

[Flash]

...DVD-R's are prescribed. Some problems are noted with other types of DVD media.

Could you be more specific? I've tried every kind of DVD media there is and as far as I can tell they were all the same.

3133, when you look at the underside of the DVD that wants you to start a new one, does it look like it is full? It's easy to see where the media has been burned. Where the burning of the latest session has stopped is usually quite apparent. The track is a continuous spiral that is burned beginning near the center of the disk and moving out toward the rim. So the part of the DVD that has been burned is toward the center. The part that is unused is toward the rim.

[3133]

Flash, thanks for advice re how DVD is burned. In my ignorance, I thought it was the other way round. In the case of the offending DVD-R, inspection shows that only about half an inch of the radius has been burned, so the disk must be faulty. Will try another. Have a large supply, so hope they are not all dud. Have had no success with DVD+R. The memory issue concerns me more. With no hard drive, I can't have a swap file, but I thought 512Mb should keep me clear of trouble. Maybe I should double that.

[Flash]

Read/write speeds are naturally higher towards the outside of the disk, which is why hard drives start from the outside. Maybe the reason optical disks start from the inside and move out is that the designers of the CD just copied the way records did it. I hope they gave the matter a little more thought than that, and decided that the rim of a removeable disk seems more likely to be damaged than the center. I haven't noticed that to be the case. Anyway, we're stuck with it now.

[Flash]

Update for Puppy 2.02beta:

Puppy 2.02beta iso downloaded and burned to a Memorex 4x DVD+R on 27 July, with a Memorex 8x burner using burniso2cd from the multisession Puppy 2alpha DVD.

A total of 94 sessions were saved to the multisession Puppy 2.02beta without incident, almost all at shutdown. (Recall that my previous multisession DVD would sometimes get into a mode which prevented saving the session at shutdown, so I usually used the "save" icon if I wanted to save anything important.)

What prompted me to start a new multisession DVD (of the latest Puppy 2.02) was that the last time I shut down the 2.02beta DVD it said that it could not save the session because that would cross the 4 GB boundary. I have to quibble with that. If I understand correctly, isofs allows the last session to cross the 4 GB (or, more correctly, the 2E32) boundary; it just won't allow a new session to start beyond that address. If this boundary does indeed apply to sessions and not just files, it might allow to save that last session while warning that the next session won't be saved. As it is, there is no warning that the disk is about to be full.

What I did to start this latest multisession 2.02 DVD was: boot the maxed-out 2.02beta DVD, then download the 2.02 iso and use burniso2cd to burn the iso to a used DVD+RW (not bothering to erase it first,) and, finally, use the "save" icon to save the first session to the newly burned DVD. When I booted the new multisession disk the first time, I had to start X from the command line but after that everything was just as if I were using the old disk.

The maximum burn speed of this DVD+RW disk is only 2x but I've found that it doesn't take very long to save even the largest sessions (the 200 MB OpenOffice iso for instance) to a 4x DVD so I don't think a 2x will slow things down intolerably.

[Flash]

Update of 2.02 on DVD+RW:

After saving the 50th session the disk developed a peculiar malady. It boots but takes forever to, and gives many many error messages of the type "Input output error" or some such, as it loads each session. ROX's "disk usage" reports that it contains 2154 Mb, but with 116 errors.

I tried booting it with the "puppy pfix=1" boot code, but no change.

Attempting to save whatever could be saved of the disk, I downloaded a fresh iso of Puppy 2.10r1 and used burniso2cd to burn it to a new DVD+RW, then, using the desktop "save" icon, saved the session to the newly burned DVD.

The new DVD booted OK, but 2.10 "restored" a lot of my settings. For instance the desktop is the Puppy 2.10 background instead of the solid buff color I had set it to in the old DVD, and I had to use the ethernet connection wizard to set up my internet connection.

All my email account settings and emails seem to have been saved. I didn't have to set my email back up, only the internet connection. There were a few jpeg images in my /root/my-documents/pictures that are gone.

I notice that the "Free Memory" display in the bottom right corner now shows 1.9G, when it was down to about 1.5G with the old disk. I deleted a few large emails and files before I saved the session, but they only added up to less than 50M at most. Where did the other 300M come from?

I'll keep the bad disk handy for a while, in case anyone has any forensic suggestions or requests.