Backup to local tape; block size and performance??
I am trying to back up a couple of file systems to local tape (/dev/
rmt0), and it's taking a VERY long time. Can someone help troubleshoot
the problem. One file system is @ 25 GB, the other is 6 GB.
I have a blocksize on the tape drive of 10240 (per an earlier
suggestion to speed up my mksysb):
# lsattr -E -l rmt0 -a block_size
block_size 1024 BLOCK size (0=variable length) True
I'm backing up via i-node to gatche the entire directory structure; my
backup command is using a blocking factor of 10, which if I read the
man page correctly, will result in a write size of 10240 (10 X 1024
block size), which is indeed a multiple of the tape's block size.
# backup -0 -u -b 10 -f /dev/rmt0 /system01
after 20 minutes of sorting things out, I see the following:
backup: There are an estimated 25031966 1k blocks.
backup: Backing up directories. This is Pass 3.
backup: Backing up regular files. This is Pass 4.
backup: 1.60% of the backup is done. It should be finished in 307:42.
And so forth....
Is there any way of calculating and/or playing about with the blocking
factor to optimize this backup? Or am I simply expecting too much of a
DLT tape drive and a 25GB backup ?
ANy thoughts/suggestions appreciated.....
Re: Backup to local tape; block size and performance??
> Is there any way of calculating and/or playing about with the blocking[color=blue]
> factor to optimize this backup? Or am I simply expecting too much of a
> DLT tape drive and a 25GB backup ?[/color]
Not really , a DLT with 6MB native should backup the 25 GB in less
then 2 hours.
> ANy thoughts/suggestions appreciated.....[/color]
Fronm this news group written in 2001
After reading some of the other responses, there seems to be some
about the tape block size versus the data buffer size (specified by
program). Setting the tape block size often doesn't have much affect,
data buffer size can make a big difference. The simplest is to set the
block size to 0 (variable), which in effect means to use a block size
the data buffer size, then use a larger buffer size with the backup
to exceed the physical buffer size of the tape drive. 64K is a good
works on most drives, but higher-speed tape drives usually perform
better if you
up it to 256 or 512K.
Even the backup program documentaion can be confusing. If they have a
to indicate a block size, they're talking about the data buffer size,
tape block size.
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Nico Lammers wrote:[color=blue]
> We have problems with our 7205 DLT tape drive (DLT4000 ).[/color]
> This drive is very sensitive to block size. For example, using a block size
> of 1024 and backing up 15GB of data will take approximately 6 hours. 15GB of
> data backed up at a block size of 120.000 will take approximately three
> hours. Small block sizes have a significant impact on performance, but only
> a minimal impact on capacity. However, 2.6 format (density) and 6 format
> (density) are significantly impacted in capacity by using small block sizes
> because they do not pack the data in the internal block. Users should ensure
> the block size they select is supported by their application. Compression
> will depend upon the type of data. A compression ratio of 2:1 is assumed for
> this compressed capacity.[/color]
> Our problem is, that it is not fast enough. Can anybody help me with the
> best configuration for this DLT 4000 for AIX 4.2 ?[/color]
Anthony Johnson 1-619-291-4500
Storix Software 1-619-291-4590 (fax)
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Weitere Optionen 18 Jan. 2001, 08:18
Von: Al Weston <alwes...@netcene.com>
Datum: 18 Jan 2001 01:17:17 -0600
Lokal: Do 18 Jan. 2001 08:17
Betreff: Re: How to configure DLT tape drive for AIX
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I've spent a lot of time tweaking DLTs and found that variable block
size with a 64k data buffer workd best I routinely get over 30 gb an
hour with this configuration.