News Group Posts

speed of restore from backup

From: "D. Thomas Podnar" <tom@microlite.com>
Subject: Re: Microlite BackupEDGE feils with error code 4.
References: <2r5D9.223$ZL2.11343@juliett.dax.net> 
Date: Fri, 22 Nov 2002 17:47:27 -0500

Rainer Zocholl wrote:
> 
>  (Ulven)  22.11.02 in /comp/unix/sco/misc:
> 
> <cut>>
> 
> >> Yuck!
> >>
> >> Travan technology sucks. Big time.
> 
> >Tell me about it!
> 
> Ask google ;-)
> 
> >> By all means, replace them with DAT. Or even SLR cartridges from
> >> Tandburg or Exabyte, depending on capacity needs and budget.
> >>
> >> SLR's are even more reliable than DAT's from my observations.
> 
> >yepps!
> 
> I know: Everybody only wants restore, nobody likes backup...but no one
> takes into account the thruput of the devices on restore...
> If it's as low as 3GB/h then a retore of only 90GB would last 30 hours
> (And a juke box if the media can't hold the 90GB)
> Almost an entire weekend...but "fatal error" occurs
> monday mornings...

Full system restores are usually more restricted by the write speed
of the hard drive than the read speed of the tape drive.

Partial restores are handled by Quick File Access.

Here's the summary of last night's backup on my main server.

(Currently using a Sony SDX-700C AIT-3)
  FILES: 205713
  Total DATA: 30.042Gb (Gigabytes)
  Actual Tape Data Written: 30.095Gb (Gigabytes)
  Elapsed Time:  47 minutes  26 seconds
  Data Transfer Speed: 11389901 bytes/sec ( 651.7 Mb/min)

Here's how long it took to restore a file 5MB from the end of
the archive on that device using Quick File Access
(we call it Fast File Restore). This includes label check,
index check and rewind times.

  mlite:root:ttyp2# time edge.restore -f tape0 /unix.test
  edge.restore: notice: getting archive information
  edge.restore: notice: beginning restore
  edge.restore: notice: wd for restore is '/'
  Reading Label From Media
  Setting Tape Blocksize/etc.
  Resource Access Started
  Opening Communications with Device
  Data Transfer In Progress
  x ./unix.test
  Operation Finishing
  Resetting Tape Parameters
  edge.restore: success (1 files)!
  real     2:04.09
  user        0.23
  sys         0.51

Each media type is different. 4mm and 8mm formats
tend to be faster than SLR formats at QFA.

> SLR can do more than 5MB/s..10MB/s IIRC, 18..36GB/h
> The above mentioned restore lasts only approx. 2,5...5h(!)
> less than one night...(if the disc, cpu and file system is fast
> enough to write that fast, sustained!).

> LTO seems to be faster(currently) and bigger. But i don't like the
> imagination the tape is again and again torn out of the (single coil)
> cartidge...
> Those SLR cassettes have a genious simple mechanism,
> the tape stays always inside the box...

Well, the concept behind LTO and DLT is that by spooling out you
can have a larger tape in the same physical space as having to
use two reels. But it works quite well, and is time-proven.

LTO/Ultrium is about the fastet device we have in our lab.
The H-P Ultrium 230 can technically back up at around 2GB/min,
but we don't have a machine that can feed it that fast. It also
has very quick QFA.
> 
> >They are located at about 40 hotels, 10 customers in Norway, Sweeden
> >and Denmark.. hehe.. :-)

Then you want to spend the extra money on highly reliable devices and
software that takes advantage of their diagnostics capabilities in order
to be able to head problems off at the pass. It also helps many newer
tape devices are "self cleaning" and you only have to insert a cleaning
cartridge on rare occasions. 
> 
> Happy journey ;-)

-- 
Best Regards,
Tom
---
  D. Thomas Podnar - President  tom@microlite.com
  Microlite Corporation         724-375-6711 Voice
  2315 Mill Street              724-375-6908 Fax
  Aliquippa PA 15001-2228       888-257-3343 Toll Free Sales
+-----------------------------------------------------------+
| Makers of                                                 |
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|  RecoverEDGE   - Network-Enabled Smart Disaster Recovery  |
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|                  and OpenServer 5.0.x.                    |
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