Saturday, November 29, 2003

QuickPar Links

QuickPar (sourceforge project page)

PowerPost (readme file)

FAQ about using binary news groups

About PAR2 (QuickPar)

Tips on how to recover a broken CD/DVD where the Table of Contents is gone

posted by Wuphon's Reach at 7:27 PM

Archiving to DVD

I've been playing around with QuickPar some more (previous post) as I finish up transferring all of my old CDR-based archives to DVD-R (packing 300 or 400 CD-Rs down to just 60-80 DVD-Rs). As a result, I've figured out a few tricks which I didn't realize last month.

1) Using the Options dialog, you should set the block size to be 1/4, 1/3, or 1/2 of your average file size. Files always get boundary-aligned, so if you have 512k files, but with block sizes of 2048k, you're going to waste 1536k for each file (efficiency value of 25%). OTOH, if you would have used 64k blocks, the average wasted space per file would only be 32k. In general, I use a block size that is 1/4 of the average file size.

2) If a file goes bad on a CD-R or DVD-R, Windows will not allow you to copy the file at all. So a single-sector ECC failure can render an entire 100Mb file unrecoverable (at least not, AFAIK, without hacking past the CD-ROM driver). Therefore, when protecting a file set, provide enough recovery data (or redundancy data) so that you can recover at least one file in the set. Making sure you can recover at least 2 files in the set would probably be safer.

2b) It's rumored that if you were to put all of the files into a single folder, and have a single PAR2 recovery set on that media, that you can rip damaged media to an ISO file, rename the ISO file to .PAR2, and QuickPar will recover the files. I've not tested it, but it's said that it's doable but since the current PAR2 spec doesn't support sub-folders that all files have to be in a single folder. (And I'm not sure if you can have multiple PAR2 sets on the same media and do the rip-to-ISO to PAR2 trick.)

3) QuickPar eats up memory when building the recovery files, so don't start 2 dozen large recovery set builds without checking how much memory is being used. I've mistakenly used up 50% more memory then I had installed in a particular machine which slowed the process to a complete crawl until I abandoned creating some of the recovery sets.

4) CFV is a good command line tool that you can use to verify PAR2 sets on a piece of media. It's main advantage is that you can easily have it recursively check all of the sub-folders on a CD/DVD. The specific command that I use to check is to CD to the root folder of the media, then issue the command "cfv -r --progress=no".

posted by Wuphon's Reach at 12:08 PM

Friday, November 28, 2003

Inhale Exhale

Right now I feel like I've just come in off a really hairy drive where it was sleeting and foggy. The adrenalin is wearing off from the stressful day that I had and my hands are shakey. The long and the short of it is that I had Thanksgiving dinner at friends of mine across town and it was apparently a much more wearing experience then I expected.

I was prepared for a certain amount of chaos since they have (3) excitable dogs and (2) young kids. The dogs are easy enough to deal with because they eventually settle down once they've greeted me. The kids, likewise, tend to be well behaved once they get over the excitement of visitors. (In general, kids want to be noticed by a visitor; so they will sometimes become boisterous as a way of getting the visitor's attention.)

As for the other people who were invited... well, it's a largish family with a few boys and a daughter and the boys are very competitive about jockeying for position. I choose not to itemize their flaws here, but there were numerous arguments throughout the afternoon, and family members who I expected to be mature and rise above the fray sometimes (often?) added to the chaos with verbal attacks.

My reaction was basically to internalize, keep a pleasant disposition, and make sure that I did nothing to escalate any of the various events. As a guest, and having just met the other family today, I decided that any intervention / interference on my part would have zero effect and that it would be better to be the placid example of calm. Leaving early would have been rather difficult because that would have added ammo to be used by the various parties ("look! you're so bad that you made their guest leave early!" ... and other varied dirty methods of fighting).

I actually thought that I was taking it quite well, letting it roll off my back like water off a duck's back, until I went to shuffle the deck of cards during the after-dinner card game. That's when I suddenly discovered that my hands were shaking from the stress. And now, 3 hours after I left I'm finding how just how emotionally drained I truly am. Ragged enough to be close to weeping, which I find surprising because I'm not sure what cause I would have to weep. More like my emotional control is extremely frayed, much like some of the more sorrowful events of my past.

I know my friends are going to check my reaction in a few days, and I have not yet come to terms with what exactly I will or won't say.

posted by Wuphon's Reach at 12:59 AM

Monday, November 24, 2003

Hard Drive Anti-Shock Mounting

I've been starting to use external USB drives (like the Part II CA405U) for backups, but I'd like to isolate the hard drives somehow within the case. Well, according to Maxtor , the hard drive screws are 6x6-32 UNC 28 threaded or 4x6-32 UNC 28 threaded. In the CA405U case, the hard drive is mounted using the bottom (4) screw holes on the drive and there's about half an inch of space above the drive. So I could easily put 1/8" or 1/4" worth of rubber grommets between the metal mounting rail and the bottom of the hard drive....

That is, if I can find the proper bits and pieces to do it.

Most drive screws seem to be between 4mm and 6mm in length and I'll need something closer to 8mm length.

Update: Well, Lowe's had some rubber washers that were 5/32" internal diameter and 3/8" external diameter and 1/16" thick which is just the right size to fit around the #6 machine screws. (A few websites sell 3/16" internal diameter 3/8" external diameter 1/6" thick rubber washers, but the 3/16" diameter is a bit larger then necessary.) The rubber washers come in packs of 2 for $0.62/pack but I haven't found anywhere to bulk order them (I figure I could probably get a pack of 100 for a few bucks).

For the screws, I found some machine screws that are 6-32 and 3/8" long (with phillips style heads). Those came in packs of 6 for $0.97/pack. If I can find 5/16" length, I'd be happier, although 1/4" length might be long enough. They also sell nylon screws which may or may not be a good idea.

My guess (and I didn't buy enough washers to test) is that to use the 3/8" long machine screws I'll need 4 rubber washers per screw to get the proper fit (1 rubber washer outside the mounting plate, 3 between the plate and the drive). I plan on running out there later this week and cleaning Lowe's out of rubber washers (grin) then I'm going to re-fit the drives inside my off-site USB backup cases.

The other idea is to find rubber hose that has a 5/32" inside diameter and make washers out of that by cutting it into bits.

Update#2: I installed a drive into the USB enclosure last night using (4) rubber gaskets and (1) 3/8" long 6-32 machine screw per hole last night and I have a few observations:

1) You'll need to use something sticky to hold the (3) gaskets in place over the hard drive mounting holes (I used electrical tape which is best) because as you lower the drive into the USB enclosure, there's no way to re-position the washers if they fall out of place.

2) The USB drive didn't have mounting holes, it had mounting "slots". This means that the rubber washers are going to twist and contort (and the 3/16" inner diameter washers would have been a nightmare). You may need to get some very thin metal washers to give the rubber washers a firm foundation.

3) Using (4) rubber gaskets on each mount point is probably over-kill, although it was necessary due to the length of the 3/8" machine screws that I used. If I used something shorter, like a 1/4" machine screw, I could have gotten away with just (2) rubber gaskets (maybe only 1 between the mounting bracket and the drive).

posted by Wuphon's Reach at 4:22 PM