Block size recommendations
Hi folks,
What's a good block size to use with tar? ie -b --blocking factor
In a hard disk to hard disk and DVD backup scheme, the term
block size gets used in at least six different ways. There are
the blocks on the source hard disk - in this case 512B in size
(at least until next year when the 4kiB drives will arrive). There
are the blocks in the source partition formats, in this case
1kiB and 4kiB in size. There is the tar blocking factor which
defaults to 20 (x512=10240 which is ancient, and some use
2048x512 which yeilds 1miB.) And then there is the block size
on the destination partitions which I'll probably set to 8kiB,
and the block size on the destination disk itself - again 512B.
And let's not forget the block size on the DVDs when I burn them.
So it's a tad confusing to know where to set the blocking factor
for tar.
On the source disk fdisk -l reveals cylinders of 16065 x 512B
for a total of 8225280 bytes. Now since 16065 factors as 119 x
135, I figure I could theoretically use a blocking factor with
tar of anywhere between 1 and 135. 20 is the default but
realistically what block size should I use?
I'm partial to a fast backup, but where lies block size
compatibility? Or is there such a thing? Ideally I'd like to
maximize disk-to-disk throughput for my backups.
b.
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