Time taken for back-up

[Ken Blake]

In my experience, the time to compress the data is less than the time
saved by the smaller amount of data to write to my USB3 external drives.

I don't know whether I've ever said it here, but I've said it many
times elsewhere: whether compression speeds up file reading and
writing depends on the relative speeds of the processor and disk
drive. In some situations it speeds it up, in others it slows it down.

 

[Gene E. Bloch]

On 2013-08-03 11:27 AM, Scott wrote:
On Sat, 03 Aug 2013 07:58:12 -0700, Ken Blake <[email protected]> []
Why does the reading speed matter? Surely reading is faster than
writing and the computer can do both as the same time?

It's the HDD that reads and writes, and no, it can't do both at the
same time.

Only if you're reading and writing from/to the same HDD, which isn't a
good backup policy, except at a secondary level.

I see my name up there in the attributions, but I didn't write
anything that you quoted.

Yes, but what were you *thinking*?

To tell the truth, I mostly have given up on expecting threads to always
remain organized. I usually try to grin (OK, scowl) and bear it, with
mixed success

 

[Gene E. Bloch]

I don't know whether I've ever said it here, but I've said it many
times elsewhere: whether compression speeds up file reading and
writing depends on the relative speeds of the processor and disk
drive. In some situations it speeds it up, in others it slows it down.

Which is one of the reasons I used the phrase "In my experience" (as
well as the word "subjective" in the part you clipped). Another reason
for "subjective" is that I haven't used a stopwatch or equivalent...

But I *know* I'm right (that's just me being ironic; of course I don't
know that).

 

[J. P. Gilliver (John)]

On 2013-08-03 11:27 AM, Scott wrote:
On Sat, 03 Aug 2013 07:58:12 -0700, Ken Blake <[email protected]> []
Why does the reading speed matter? Surely reading is faster than
writing and the computer can do both as the same time?

It's the HDD that reads and writes, and no, it can't do both at the
same time.

Only if you're reading and writing from/to the same HDD, which isn't a
good backup policy, except at a secondary level.

I see my name up there in the attributions, but I didn't write
anything that you quoted.

Sorry, I snipped one too few lines. (In my defence I'd point out that
not enough - often not any - snippage is being done here, so my error is
understandable even if not forgivable!)
--
J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

I'm not a fan of Christmas, although I support the principle of a day of
feasting and presents, but the anxiety starts in October: how many are coming?
Are they bringing grandchildren? How long will they stay? - Raymond Briggs, in
Radio Times Christmas 2012

 

[Ken Blake]

In message <[email protected]>, Ken Blake

Sorry, I snipped one too few lines. (In my defence I'd point out that
not enough - often not any - snippage is being done here,

Right. I'm with you completely!

so my error is
understandable even if not forgivable!)

Your error is both understandable and forgivable. No big deal. I just
didn't want anyone else to think I wrote something I didn't.

 

[Ken Blake]

Yes, but what were you *thinking*?

To tell the truth, I mostly have given up on expecting threads to always
remain organized. I usually try to grin (OK, scowl) and bear it, with
mixed success

Expecting? No, I don't expect too much either. But I try to correct
such an error when I notice it.

 

[Ken Blake]

Which is one of the reasons I used the phrase "In my experience" (as

Understood. I wasn't disagreeing with you, just pointing out that
everyone's experience isn't the same here. It depends on the hardware.

 

[Paul]

In message <[email protected]>, Wolf K
On 2013-08-03 11:27 AM, Scott wrote:
On Sat, 03 Aug 2013 07:58:12 -0700, Ken Blake <[email protected]>
[]
Why does the reading speed matter? Surely reading is faster than
writing and the computer can do both as the same time?
It's the HDD that reads and writes, and no, it can't do both at the
same time.

Only if you're reading and writing from/to the same HDD, which isn't a
good backup policy, except at a secondary level.

Well, yeah, but then one disk reads, and the other writes. Neither can
do both at the same time....

Have a good day.

The real question is whether the controller(s) and the DMA (or whatever
passes for that in the 21st century: I'm pretty much 20th century
m'self) can do both at the same time, one process each on two separate
drives...

On two disks, I/O can overlap.

I've seen it overlap while using Robocopy.

To test, make a large test file with "dd" (as fsutil likes to make
sparse files), then fire up Performance Monitor, and watch what
happens during a Robocopy. That should be sufficient to
prove or disprove the availability of non-blocking I/O.

******

As for DMA, it may be time multiplexed over DMI, but
there is sufficient capacity on DMI bus, for trivial
(non-RAID, non-SSD) cases. The multiplexing would happen
in a test case where you ran HDTune read benchmark on
one disk, and HDTach read benchmark on a second disk,
at the same time. The DMA agents interleave on the bus.
If you did a four disk RAID0 on the SATA2 ports, and
a two disk RAID0 on the SATA3 ports, used SSDs for all,
you might actually bump your head on the DMI bus limit,
while read benching both.

SATA and PCI Express are full-duplex, which allows a certain
amount of read-on-one-disk, write-on-another-disk testing,
to not fight for resources. (The interfaces have separate
transmit wires and receive wires.) Even DMI is full duplex.
So the plumbing is definitely more capable, than back in
the year 2000, when the entire Southbridge (and all your
IDE cables), were hosted over the bandwidth of a single
simplex ~110MB/sec PCI bus. That's why those old computers
sucked at I/O.

Paul

 

[Paul]

Understood. I wasn't disagreeing with you, just pointing out that
everyone's experience isn't the same here. It depends on the hardware.

It depends on the content.

If you have a movie disk (a format already 100:1 compressed),
there is no entropy to harvest, and turning on the Macrium
compression option, would be a waste of your time. Time
wasted, no space saved.

Very few users now, will have content disks, with nothing but
uncompressed files on it. My computer back in 1985 would have
been ideal for such compression ideas, but now, not so much.

Things like PDF or movies, won't compress that much. Might take
7Z to make progress, and 7Z is slow as molasses. You wouldn't want
Macrium to be using 7Z for you. Good space, poor time tradeoff.

Macrium uses a lightweight LZ compressor, which is a good space-time
tradeoff for a backup (it would be like GZIP, but lighter). Just
don't expect miracles for a disk full of movies. It will compress
a text file for you, but won't be able to do much with other file
types.

Without benching it here, I'd probably keep it turned off.
Just knowing the content of the disks.

It would also depend, on whether their LZ compressor was
multi-threaded or not. Standard GZIP is not, so you can have
a six-core processor, and GZIP would only use one core. Before
"hoping" your hardware would be overpowering, and crush the problem,
better check whether it's threaded. I only have one compressor
(PIGZ), which is multithreaded and does GZIP. (7ZIP only uses
multiple threads for 7Z, and is still single threaded for GZ.)
I don't know if Macrium does threading or not. Run Macrium, use
Task Manager, and you might get a hint. If you turn on compression,
and the CPU is pegged on all cores, you have your answer.

Paul

 

[Wolf K]

On 2013-08-03 11:27 AM, Scott wrote:
On Sat, 03 Aug 2013 07:58:12 -0700, Ken Blake <[email protected]> []
Why does the reading speed matter? Surely reading is faster than
writing and the computer can do both as the same time?

It's the HDD that reads and writes, and no, it can't do both at the
same time.

Only if you're reading and writing from/to the same HDD, which isn't a
good backup policy, except at a secondary level.

I see my name up there in the attributions, but I didn't write
anything that you quoted.

Sorry, I didn't proofread the attributions before I hit Send. ;-(

 

[Gene E. Bloch]

On two disks, I/O can overlap.

I thought I might have said that

 

[Gene E. Bloch]

Understood. I wasn't disagreeing with you, just pointing out that
everyone's experience isn't the same here. It depends on the hardware.

OK, understood & accepted.

Now please forgive me for complaining

 

[slate_leeper]

Basic question I know, but why does a back-up using Norton Ghost take
more than two hours? I thought computers carried out millions of
calculations every second. Is it to do with the writing time to the
back-up disc?

I have significantly speeded up backups by turning off file scanning
in my antivirus program while the backup is running. Don't forget to
turn it back on when done.

-dan z-



--
Protect your civil rights!
Let the politicians know how you feel.
Join or donate to the NRA today!
http://membership.nrahq.org/default.asp?campaignid=XR014887

Gun control is like trying to reduce drunk driving by making it tougher for sober people to own cars.

 

[Ken Blake]

In message <[email protected]>, Wolf K
On 2013-08-03 11:27 AM, Scott wrote:
On Sat, 03 Aug 2013 07:58:12 -0700, Ken Blake <[email protected]>
[]
Why does the reading speed matter? Surely reading is faster than
writing and the computer can do both as the same time?

It's the HDD that reads and writes, and no, it can't do both at the
same time.

Only if you're reading and writing from/to the same HDD, which isn't a
good backup policy, except at a secondary level.

I see my name up there in the attributions, but I didn't write
anything that you quoted.

Sorry, I didn't proofread the attributions before I hit Send. ;-(

OK, not a big problem.

Ken

 

[Shoe]

OK, understood & accepted.

Now please forgive me for complaining

My computer is old enough that it does not have USB3. I found that I
could add a USB3 card with two ports and connect a USB3 external drive
to this. The card and a USB3 docking station together cost about $50.
The reduction in time needed for a backup was amazing, like from all
night to 2 hours. This is worth a try if you are not using USB3.

 

[choro]

.]

Now please forgive me for complaining

My computer is old enough that it does not have USB3. I found that I
could add a USB3 card with two ports and connect a USB3 external drive
to this. The card and a USB3 docking station together cost about $50.
The reduction in time needed for a backup was amazing, like from all
night to 2 hours. This is worth a try if you are not using USB3.

But had you waited another few months you could have probably bought the
card for around 20 bucks!

 

[Gene E. Bloch]

My computer is old enough that it does not have USB3. I found that I
could add a USB3 card with two ports and connect a USB3 external drive
to this. The card and a USB3 docking station together cost about $50.
The reduction in time needed for a backup was amazing, like from all
night to 2 hours. This is worth a try if you are not using USB3.

I've been using USB3 for at least a year...I did mention above in this
subthread that I am using USB3: "...my USB3 external drives".