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Gentoo on Hyper-V horrible Hdd Latency
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Mrifao
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Joined: 05 Dec 2015
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PostPosted: Sat Dec 05, 2015 9:06 pm    Post subject: Gentoo on Hyper-V horrible Hdd Latency Reply with quote

Hi
Install the Gentoo on Hyper-V (Winsows Serwer 2012 R2).
I have the problem of disk latency. What I can do to improve the Hdd performance.
The OS Windows stay on Raid 1 by SAS Hdd 15k.


root@fdm 20:08:59 ~ dd if=/dev/zero of=testfile bs=512 count=4096 oflag=dsync
4096+0 records in
4096+0 records out
2097152 bytes (2.1 MB) copied, 154.771 s, 13.6 kB/s
root@fdm 20:27:38 ~ dd if=/dev/zero of=testfile bs=1024k count=4096 oflag=dsync
4096+0 records in
4096+0 records out
4294967296 bytes (4.3 GB) copied, 188.157 s, 22.8 MB/s
root@fdm 20:44:45 ~


Have you any idea?
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Keruskerfuerst
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Joined: 01 Feb 2006
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Location: near Augsburg, Germany

PostPosted: Sun Dec 06, 2015 11:03 am    Post subject: Reply with quote

Why do you install not directly on the machine?

Why a Hyper-V?
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HerbMillerJW
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PostPosted: Sun Dec 06, 2015 12:51 pm    Post subject: Reply with quote

What filesystem?
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jfp
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Joined: 08 Jul 2007
Posts: 279
Location: Virginia, USA

PostPosted: Sun Dec 06, 2015 2:06 pm    Post subject: Reply with quote

Just for something to compare to. I ran your dd commands on a real (although not especially powerful) gentoo server. The results are below.

Code:
john@NASHost ~ $ dd if=/dev/zero of=testfile bs=512 count=4096 oflag=dsync
4096+0 records in
4096+0 records out
2097152 bytes (2.1 MB) copied, 189.509 s, 11.1 kB/s
john@NASHost ~ $ rm testfile
john@NASHost ~ $ dd if=/dev/zero of=testfile bs=1024k count=4096 oflag=dsync
4096+0 records in
4096+0 records out
4294967296 bytes (4.3 GB) copied, 155.637 s, 27.6 MB/s

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jfp
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Cyker
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Joined: 15 Jun 2006
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PostPosted: Sun Dec 06, 2015 6:12 pm    Post subject: Reply with quote

Well smeg... you're both doing loads better than me! :(

Code:

$ dd if=/dev/zero of=testfile bs=512 count=4096 oflag=dsync
4096+0 records in
4096+0 records out
2097152 bytes (2.1 MB) copied, 297.058 s, 7.1 kB/s

$ dd if=/dev/zero of=testfile bs=1024k count=4096 oflag=dsync
4096+0 records in
4096+0 records out
4294967296 bytes (4.3 GB) copied, 378.205 s, 11.4 MB/s


This is on an AMD APU A10-7850K with 16GB RAM and the file system is a btrfs RAID6 connected to A88X chipset SATA channels...
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Ant P.
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Joined: 18 Apr 2009
Posts: 5761

PostPosted: Mon Dec 07, 2015 1:06 am    Post subject: Reply with quote

I may as well add some more numbers -
AMD E-350, 1×SSD, Btrfs, BFQ:
~ $ dd if=/dev/zero of=testfile bs=512 count=4096 oflag=dsync
4096+0 records in
4096+0 records out
2097152 bytes (2.1 MB) copied, 38.7575 s, 54.1 kB/s
~ $ dd if=/dev/zero of=testfile bs=1024k count=4096 oflag=dsync
4096+0 records in
4096+0 records out
4294967296 bytes (4.3 GB) copied, 73.4171 s, 58.5 MB/s

To answer the original question: simple, don't force sync in ridiculously small intervals.
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Mrifao
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Joined: 05 Dec 2015
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PostPosted: Mon Dec 07, 2015 3:09 pm    Post subject: Reply with quote

Hi
Now for answers
Why - it is long story about someone who have idea of It solution, someone make order and someone try to do :P

About file system[/quote]
Hyper V
- 40 Gb fo system, Ntfs, 4096 block
- 30 GB for pagefile, Ntfs, 4096 block
- 60 Gb for virtual system , ntfs, 4096 block

Gentoo
FileSystem, type, 1K-blocks
/dev/root, ext4, 40894800
devtmpfs, devtmpfs, 10240
tmpfs, tmps, 1230496
shm, tmpfs, 6152480
cgroup_root, tmpfs, 10240

And test from debian 7 instaled direcly on similar serwer

> dd if=/dev/zero of=/root/testfile bs=1G count=1 oflag=dsync
1+0 przeczytanych recordów
1+0 zapisanych recordów
skopiowane 1073741824 bajty (1,1 GB), 4,83221 s, 222 MB/s

> dd if=/dev/zero of=/root/testfile bs=512 count=1000 oflag=dsync
1000+0 przeczytanych recordów
1000+0 zapisanych recordów
skopiowane 512000 bajtów (512 kB), 15,2765 s, 33,5 kB/s
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