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Bug #7901

Devices that do not support setting WC keep generating ereports

Added by Yuri Pankov about 3 years ago. Updated about 3 years ago.

Status:
Closed
Priority:
Normal
Assignee:
Category:
driver - device drivers
Start date:
2017-02-22
Due date:
% Done:

100%

Estimated time:
Difficulty:
Medium
Tags:

Description

Description by Jeffry Molanus.

There is a very long outstanding issue around zeus rams and perhaps others, where the system tries to enable the Write Cache (WC).

This generates an ereport on each vdev_disk_open() and the ereport DB can grow substantially over time with lots of reports indicating the problem.

Also, the ereports trigger other parts of the system to kick in gear in particular FMD and we could really spare the IOPs and CPU cycles if we become a little smarter when handling the DKIOCSETWCE ioctl.

Using dtrace is easy to find out what disk and operation is causing the error

CPU ID FUNCTION:NAME
4 32548 scsi_transport:entry
sd`sd_start_cmds+0x25f
sd`sd_core_iostart+0xf7
sd`sd_uscsi_strategy+0x15f
genunix`default_physio+0x33d
genunix`physio+0x25
scsi`scsi_uscsi_handle_cmd+0x2a5
sd`sd_ssc_send+0x195
sd`sd_send_scsi_MODE_SELECT+0x1ca
sd`sd_cache_control+0x3d4
sd`sdioctl+0x1bfb
genunix`cdev_ioctl+0x39
genunix`ldi_ioctl+0x88
zfs`vdev_disk_open+0x297
zfs`vdev_open+0x1d5
zfs`vdev_open_child+0x28
genunix`taskq_thread+0x318
unix`thread_start+0x8

When we issue the MODE SENSE(10) we should prior to that set the page control field to 1, and verify the setting is changeable before we just blindly modify the bit. the STEC zeusram does not support changing this bit and as result we generate sense data which triggers the ereport over and over and over again as we dont learn from our failures.

History

#1

Updated by Yuri Pankov about 3 years ago

  • Description updated (diff)
#2

Updated by Electric Monk about 3 years ago

  • Status changed from In Progress to Closed
  • % Done changed from 50 to 100

git commit f1cc607eb9fe881d3fa29a24921e6ba1b64eb7fb

commit  f1cc607eb9fe881d3fa29a24921e6ba1b64eb7fb
Author: Jeffry Molanus <jeffry.molanus@nexenta.com>
Date:   2017-03-02T14:08:42.000Z

    7901 Devices that do not support setting WC keep generating ereports
    Reviewed by: Yuri Pankov <yuri.pankov@nexenta.com>
    Reviewed by: Dan Fields <dan.fields@nexenta.com>
    Reviewed by: Robert Mustacchi <rm@joyent.com>
    Approved by: Hans Rosenfeld <rosenfeld@grumpf.hope-2000.org>

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