Marvin Müller
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Posts posted by Marvin Müller
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Dear all,
I have a hypervisor with (fully patched) XenServer 7.6 (E5-2620 v4, 32GB, LSI 9750-4i, 2x Samsung SM883 SSD). Looking at Dom0, I get reasonable read/write speeds:
[root@localhost ~]# dd if=/dev/sda of=/dev/zero bs=1M count=1024 1024+0 records in 1024+0 records out 1073741824 bytes (1.1 GB) copied, 1.0037 s, 1.1 GB/s
[root@localhost ~]# dd if=/dev/zero of=/root/testfile bs=1M count=1024 1024+0 records in 1024+0 records out 1073741824 bytes (1.1 GB) copied, 1.89972 s, 565 MB/s
[root@localhost ~]# hdparm -tT /dev/sda /dev/sda: Timing cached reads: 21612 MB in 1.97 seconds = 10965.82 MB/sec Timing buffered disk reads: 3124 MB in 3.00 seconds = 1041.28 MB/sec
The controller does not have a BBU enabled. I did multiple runs, they result in pretty much equal speeds.
Now looking at a Ubuntu 16.04 VM:
root@server:/home/toor# dd if=/dev/xvda of=/dev/zero bs=1M count=1024 1024+0 records in 1024+0 records out 1073741824 bytes (1,1 GB, 1,0 GiB) copied, 1,18745 s, 904 MB/s
root@server:~# dd if=/dev/zero of=/root/testfile bs=1M count=1000 1000+0 records in 1000+0 records out 1048576000 bytes (1,0 GB, 1000 MiB) copied, 10,3562 s, 101 MB/s
The guest is HVM, installing Xen Tools did not help much. All Hypervisor settings are default, same on the guest.
I read through several threads, but most of them covering slow read and write access. I have a second host with a similar setup with the same controller. Any advice how to speed up writes is highly appreciated. Thank you very much!
Slow write speeds in DomU on LSI SSD RAID, read ok
in Guest Runtime
Posted
Thanks very much for the input. I did further runs with bonnie++ with similar results. It seems that the root cause was the array not yet being fully in sync. After now being in good health, performance is much better.
Marvin