Cejka Rudolf wrote (2017/06/05):
> Cejka Rudolf wrote (2017/06/02):
> > Ivan Adzhubey wrote (2017/06/01):
> > > b) What is the effect of MaximumFileSize option and what would be its
> > > optimal
> > > value for my IBM LTO-5 SAS drives? I have used 8GB value found in one of
> > > the
> > > list posts, while the documentation suggests 2GB for LTO-4. But even set
> > > at
> > > 8GB this would create lots of EOF marks on a 1.5TB tape, do we really
> > > need so
> > > many?
> >
> > Hi, I do use 16 GB. Every EOF mark means around 3 seconds delay. So if you
> > have
> > over 200 files on the tape using 8 GB, it is around 10 minutes extra per
> > tape.
>
> Hi, small fix. It seems that it is even around 5-6 seconds delay resulting in
> extra 20 minutes per tape. And worse, I'm afraid that the tape drive do not
> stop nor slowdown tape movement, which would mean over 10 % of the tape lost
> because of filemarks. Hope that I'm wrong.
Hi, I finally have done and finished real testing with Maximum File Size option.
Tested on LTO-6 drive with LTO-5 tape, so the results are relevant for LTO-5,
used btape utility and fill s (simplified) command.
Fortunately, I has negligible impact on tape capacity, but unfortunately, I has
really dramatical impact on overall write speed and you have to count not just
5-6
seconds, but better 8-10 seconds per file. I also added time to read one file at
140 MB/s, which is important for seeking during restores.
File Simplified Simplified Bytes Files Rough time to
size fill time fill rate written written read one file
1 GB 6:44:18 61.8 MB/s 1498688192512 1499 00:00:07
2 GB 4:51:30 85.7 MB/s 1498737278976 750 00:00:14
4 GB 3:54:57 106.3 MB/s 1498762641408 375 00:00:29
8 GB 3:24:22 122.2 MB/s 1499224932352 188 00:00:57
16 GB 3:11:09 130.7 MB/s 1499456405504 94 00:01:54
32 GB 3:04:35 135.4 MB/s 1499690303488 47 00:03:49
64 GB 3:01:17 137.8 MB/s 1499574960128 24 00:07:37
128 GB 2:59:37 139.1 MB/s 1499603664896 12 00:15:14
And it seems that the results are perfectly reproducible. Three successive
tests with 16 GB file size have had exactly the same fill time 3:11:09!
Tests were done by mistake, when I wondered how it is possible that the
time stays exactly the same :o)
Regards.
--
Rudolf Cejka <cejkar at fit.vutbr.cz> http://www.fit.vutbr.cz/~cejkar
Brno University of Technology, Faculty of Information Technology
Bozetechova 2, 612 66 Brno, Czech Republic
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