Re: [Dump-users] problem with restore

[Stelian P. <st...@po...>]

Le lundi 19 février 2007 à 10:52 +0100, Jean-Yves Boisiaud a écrit :
> Hello,
> 
> I use dump to backup a large file system to a LTO2 tape changer.
> 
> The system is a debian Sarge running a 2.6.8-3-686-smp kernel.
> The hardware is a HP LTO-2 tape drive with an Overland LoaderXpress tape 
> changer. The system have 2 GB or RAM and a swap of 2 GB too.
> 
> Version of dump/restore is the last one (dump 0.4b41 (using libext2fs 
> 1.37 of 21-Mar-2005)), compiled by my own.
> 
> The file system is ext3, its size is 1.3 TB with 300 GB to backup.
> Data to backup comes from BackupPC, a simple by efficient backup on disk 
> system.
> 
> Dump works perfectly. Here is the command I run :
> 
> /usr/local/sbin/dump -0 -b 64 -f /dev/st0 -M -F \
>      /usr/local/sbin/save_tape_change.sh -I 0 /dev/lvm0/backuppc
> 
> The script save_tape_change.sh drives the tape changer.
> Data are dumped to tapes in 4h49m.
> 
> The problem is when I run restore to check tapes are OK.
> Here is the dump command I run :
> 
> /usr/local/sbin/restore -r -y -b 64 -f /dev/st0 -M -F  \
>      /usr/local/sbin/save_tape_change.sh -N
> 
> And restore takes hours, fulling memory and swap.
> 
> My question is how could I run restore in the same time dump takes ?

You won't be able to run it "in the same time" for the simple reason
that while dump accesses the raw filesystem (which is quite optimal),
restore does the filesystem accesses in a pure standard way (using
open/read/write etc). So it is normal for restore to be an order of
magnitude slower than dump.

> How much memory I need (or how could I compute the memory needed) ?

You need at least enough memory to handle the inode maps (2 binary maps,
each being max_ino bits in size). But this is a constant amount, once
allocated it shouldn't grow up much during the execution.

But restore also uses plenty of space in /tmp (well, TMPDIR) to cache
the whole directory structure of the filesystem being restored. Is /tmp
on your systems backed by disk or memory space (tmpfs ?) ?

-- 
Stelian Pop <st...@po...>