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Re: [edlug] DVD RW disks for backup - advice - response




Andrew,


I've had a go with Packet Writing to CD/RW (CD-R is not yet supported on Linux) and it works well, if a little slow. With the 2.4 kernel you add the packet writing patch, format the CD-RW with a UDF filesystesm and copy/delete files.

I've tried UDF on DVD too. The DVD alternative is ISO9660 but it starts to get a bit flaky past 4Gb, because the discs are 4.7Gb and directories past the 4Gb limit are not permitted. I've not tried ISO9660 on DVD for this reason.

Packet writing large files to a UDF format optical disc on the 2.4 kernel will crash your system. Large means any file bigger than physical memory. What happens is the HDD fills all available memory with disk buffers waiting to be written to the optical media. They can't be swapped out becuse they are 'dirty buffers'. The system dies as a result. Provided the data to be transferred fits into memory, things are OK.

This is supposed to be fixed in 2.6 but I'm waiting for it to stop changing so fast to put it to the test.

There is a useful mailing list here packet-writing@xxx.xxx.xxx

Hope that helps,

Roy Bamford


On 2004.03.16 19:45, Andrew Smith wrote:

Hi Ed


You understood exactly what I'm wanting to do, which is to take a snapshot of a set of files. The PCPLUS review is fine for getting rough prices and the capabilities good and bad of each drive. I'm thinking of getting the new LG drive as it also does DVD-RAM. Then I think its a decode of how cdrecord works, a lot of reading,some experiments and if it works my contribution to OSS. If anyone wants to pitch in and help or suggestions, that will be welcome. I've got the time and facilities, but not necessarily the energy.

--
Andrew
Ed wrote:

True, but you still need removable media to recover deleted files or to cope with disasters.
My (limited) understanding is that any drive which can write -RAM or +/-RW media can do packet writing and so the compatibility is a software matter, older drives may need firmware upgrades. Last I heard the packet writing patches for Linux resulted in dreadful performance so that may be a concern.


The most recent issue of PC-Plus out today has a group review of DVD writers.

Ed
-----Original Message-----
From: "A. Zelter" <azelter@xxx.xxx.xxx>
To: asmith@xxx.xxx.xxx
Date: Mon, 15 Mar 2004 12:56:13 -0800 (PST)
Subject: Re: [edlug] DVD RW disks  for backup - advice

Wouldn't software RAID be cheaper and easyer and better than a DVD every
night?


Cheers,

Alex

I'm considering buying buying a DVD writer and using RW disks for an overnight
backup using cron and a script.


I'm fine with mkisofs and cdrecord for CD-RW disks.
What packages do I need for DVDs ?

Should I get a drive capable of packet writing ?


--


Andrew
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