So, we had a muli-disk failure in a hardware RAID rendering our system down. No problem, we'll just slip in a new box, install Linux and recover our data from backup tape. Being called into this situation from the outside, the facts behind the backup method are very fuzzy - possibly "cpio". When I run "cpio -itv -I/dev/st0" on the tapes, I am treated to "cpio: read error: Cannot allocate memory" ... I've tested creating a cpio archive and reading from it - no problem. Every tape in their box yields the same result. The local admin says the results were displayed each morning - successful! Not sure how/what was being done to determine this. Now the basic question I'm posing: Is there any way to determine what the archive type on the tape is? In SCO I would have simply run: dtype /dev/rStp0 and it would spew the type of archive ... tar, cpio, unknown, etc. I am using RedHat Enterprise ES 4.0 - fully up2date. The tape drive is a Dell PowerVault 110 (DLT) and the controler is an Adaptec 7xxx (64-bit stuck into a 32-bit PCI slot).

Thanks in advance!

I'm familiar with some of backup methods used with linux. Probably the most popular is with tar. TAR stands for Tape ARchive. Most backups are raw, or tar. To get the data off the drive you can use "dd" and pipe the output to "tar". This is done like this:

<dd if=/dev/st0 ibs=<tapeblocksize> | tar xv | dd of=/dev/<diskdevice> obs=<diskblocksize> conv=notrunc,noerror>

If the tape is raw:

<dd if=/dev/st0 of=/dev/<diskdevice> ibs=<tapeblocksize> obs=<diskblocksize> conv=notrunc,noerror>

Block sizes for disks are 512. You can use a multiple also. obs=8b would be 8x512 or 4096 bytes. This is typically a good block size for disk.

I'm not sure which block size your tape drive uses. It is the size of one sector. I'm not sure if one can use multiple blocks at a time with a tape drive. Some tape drives have apparently weirdly conceived block sizes. I'm not sure why there is not standardization between tape and disk drive block sizes.

if they are using RH enterprise, they probally are entitled to some tech support from rh?


if so, let us know what you come up with. if not, hopefully sombody who knows more than me about tape backups reads this soon :P