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Re: Backup
On Sun, 26 May 1996 17:17:52 +0300, you wrote:
>===> Udi Finkelstein writes on May 26, 8:49am :
>===>
>===> Subject : Re: Backup
>==>
>=> On Sun, 26 May 1996 04:52:29 GMT, you wrote:
>=>
>=> <stuff deleted here>
>=>
>=> So far I'm checking KBackup 1.2.7 and taper 6.X.X, both are free.
>=> taper seems more robust (written in C), but it creates it's own format (which
>=> scares me), and not very fast. I was disappointed when it measured a backup
>=> speed of 12-13MB/min, when I get 30MB/min under NT with NT Backup ("Backup
>=> Exec Lite...").
>=>
>=> <stuff deleted here>
>=>
>==>
>===> end of the message of Udi Finkelstein.
>
>I am not sure how you measured the backup speed.
>13MB/min = 780MB/hour is greater than backup speeds for the most advanced
>DAT (4mm) tape drives (without compression). Theses have 500MB/hour.
All DDS1 tapes from all the companies are doing 180KB/sec, which amounts to
648MB/h.
If you are using compression (DDS1-DC), then your speed goes up proportionally
to the compression factor of the data you are backing up, since the limiting
factor is the raw data R/W rate. If you do H/W compression before writing, you
gain bandwidth.
HP's DDS2 tapes have 510KB/sec ***RAW MEDIA SPEED***. Yup, that's 3 times
faster than everyone else's DDS1 tapes. That means 1.8GB/h.
I think that SOME companies MAY give you 384KB/sec on their DDS2 drives, but
none gives you 510KB/sec like HP.
The speed improvements is also for DDS1 and DDS1-DC media, not only for DDS2
media. In fact, using DDS1-DC you may get as much as 1MB/sec due to
compression.
As I said, I am constantly getting these speeds using normal DDS1 media
without ANY hardware compression. (I want my media to be readable by ALL
drives, and I've heard about DDS1-DC incompatibilites. Media is so cheap I
don't care about the extra capacity with DDS1-DC. I bought a DDS2 drive only
because it does 500KB/sec).
>You may be backuping to a faster device, or the NT software is cheating
>with its throuput report, or maybe you are not using compression on Linux.
Nope. The compression is off, the NT numbers are true, and I have to get AFIO
to get some real benchmarks on KBackup... yup, that's the real story!
>Gili
Udi
References:
- Re: Backup
- From: gil@csc.cs.technion.ac.il (Gili Granot)