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Re: [Bug-ddrescue] Slowness during recovery

From: Antonio Diaz Diaz
Subject: Re: [Bug-ddrescue] Slowness during recovery
Date: Tue, 23 Dec 2008 20:12:03 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i586; en-US; rv:1.7.11) Gecko/20050905

colo wrote:
But I think the big question is what is the theoretical average top speed this can produce?

More or less the maximum the drive can reach. For example:

# hdparm -t /dev/hda
 Timing buffered disk reads:    4 MB in  3.58 seconds =   1.12 MB/sec

$ ddrescue -v test_file /dev/null
About to copy 123193 kBytes from test_file to /dev/null
    Starting positions: infile = 0 B,  outfile = 0 B
    Copy block size: 128 hard blocks
Hard block size: 512 bytes
Max_retries: 0
Direct: no    Sparse: no    Split: yes    Truncate: no

Press Ctrl-C to interrupt
rescued:   123193 kB,  errsize:       0 B,  current rate:     393 kB/s
   ipos:   123142 kB,   errors:       0,    average rate:     938 kB/s
   opos:   123142 kB

This is on an old AMD K6 with a 20GB drive and yields about 56MB per minute. My Atlon64 gives 3.35MB/s (201MB/min) and ddrescue copies on it at 3.4MB/s (205MB/min).

Can it ever do 10 megs a minute? At 10 megs a minute for a typical 500gig hard drive it could take 34 days.

As you can see it all depends on the drive. If it is damaged, the speed can be arbitrarily slow.

Best regards,

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