Hi,
Thank you, Rudolf. This is very useful information! Thank you for taking effort
to benchmark this.
Best,
Ivan
On Friday, June 23, 2017 03:53:04 PM Cejka Rudolf wrote:
> 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.
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