From mboxrd@z Thu Jan 1 00:00:00 1970
From: bugzilla-daemon@bugzilla.kernel.org
Subject: [Bug 42939] New: hv_storvsc - write cache enabled by default and
cannot be disabled
Date: Thu, 15 Mar 2012 21:56:00 GMT
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https://bugzilla.kernel.org/show_bug.cgi?id=42939
Summary: hv_storvsc - write cache enabled by default and cannot
be disabled
Product: SCSI Drivers
Version: 2.5
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: Other
AssignedTo: scsi_drivers-other@kernel-bugs.osdl.org
ReportedBy: bugzilla-kernel-org-sux2k0@mstier.de
Regression: No
dmesg output:
[ 8.080401] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled,
supports DPO and FUA
Question: how safe is my (database) data in the case of a host machine crash or
a VM crash?
There is no battery-backed writecache installed in the host, just some cheap
and slow SATA disks.
Another curiosity occurs when running the fio iometer benchmark on the same
machine: it gives me 5.000 to 6.000 I/O random access operations per second
when using the para-virt hv_storvsc driver, but only the expected 200 I/O ops
when using ata_piix via emulation.The kernel in question is version 3.2.11.
There doesn't seem to be any way to disable the para-virt device's write-cache.
Kernel version is mainline 3.2.11.
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