Avoid tar for Dell PowerVault 100T DAT 72 tape drive?

Chuck Swiger cswiger at mac.com
Tue Oct 12 11:03:37 PDT 2004

Tom Oak wrote:
> The user's guide for the Dell PowerVault 100T DAT 72 tape drive recommends 
> against using tar (see quoted text below). Does anyone have any experience
> with this product and can advise whether we should avoid tar? Thank you for
> your help.

The concern they have is valid, as tar defaults to using a tiny block size 
(512 or 2048 bytes, depending), which will cause the tape drive to start and 
stop rather than stream.

Fortunately, you can either pipe tar into dd to change the blocksize, or else 
change the blocksize to something larger using the -b (--block-size for 
gnutar) option.  For what it's worth, I've been using a blocksize of 126 (* 
512, or 63K) with DLT drives for years now.  Why 63K is (or was) faster than 
32K or 64K or other values is not at all clear to me :-), so do your own 
testing to see.


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