Bug 42939
Summary: | hv_storvsc - write cache enabled by default and cannot be disabled | ||
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Product: | SCSI Drivers | Reporter: | Mark (bugzilla-kernel-org-sux2k0) |
Component: | Other | Assignee: | scsi_drivers-other |
Status: | NEW --- | ||
Severity: | normal | ||
Priority: | P1 | ||
Hardware: | All | ||
OS: | Linux | ||
Kernel Version: | 3.2.11 | Subsystem: | |
Regression: | No | Bisected commit-id: |
Description
Mark
2012-03-15 21:55:58 UTC
Additional information: trying to disable the writecache leads to the partition on the SCSI device getting remounted read-only due to device errors. Additional information (2): I get 5.000 to 6.000 random reads per second even when manually creating the fiometer file using random data from /dev/urandom (ie. fio doesn't access zeroes in that case). Additional information (3): The host doesn't seem to cache anything: "dd iflag=direct if=/dev/sda bs=1M of=/dev/null count=10" always and repeatedly gives me around 30-60 MB/s. Additional information (4): I did a simple MySQL InnoDB ACID transaction test where subsequent transactions are done via a remote mysql client as fast as possible. I crashed the host hardware and checked if all transactions reported as completed had been committed to disk: no obvious problems there -- seemingly the reported writecache has no writecache-effects at all...?? Additional information (5): I'm getting 1.000 subsequent (serialized and small -- integer inserts) transactions done (locally) within 2.2 seconds -- with InnoDB ACID transactions (ie. full data transaction sync enabled). Isn't that a bit too fast for cheap SATA disks in a RAID10 config? |