PE1850 / PERC 4e/Si / RHEL4 problem
jetkins at austinlogistics.com
Tue May 9 13:33:16 CDT 2006
Actually, it's a correct assumption at the driver level. The driver
assumes write-through, which means that any data that it passes to what
it sees as a physical disk (but is in fact the cache-backed RAID
controller) is guaranteed to be written to the disk before the I/O is
completed. The fact that it may actually reside temporarily in the
battery-backed controller cache before actually being written to the
underlying physical media is immaterial to the driver - it's been
delivered to the disk subsystem and WILL be written to the drive.
Network & IT Administrator
Austin Logistics, Incorporated
From: linux-poweredge-bounces at dell.com
[mailto:linux-poweredge-bounces at dell.com] On Behalf Of J. Epperson
Sent: Tuesday, May 09, 2006 12:10 PM
To: linux-poweredge at dell.com
Subject: Re: PE1850 / PERC 4e/Si / RHEL4 problem
"Without this information, the block layer assumes "write-through". This
is safe, because the controller has a battery-backed cache.".
Write-through is safe WITHOUT a battery-backed cache--the block layer is
treating you as though you DON'T have one. The battery-backed cache
protects you in "write-back" mode.
"...it's not an error, and it doesn't affect the system."
Other than delaying your boot by at least a minute, only to make an
The information contained in and transmitted with this email, including any attachments, is confidential and/or proprietary information of Austin Logistics Incorporated, and is intended only for a specific addressee or addressees. If there is an agreement concerning the treatment of confidential or proprietary information in force between Austin Logistics Incorporated and the recipient, this message and any attachments shall be treated as confidential in accordance with the terms of such agreement. Any dissemination, distribution, copying, or use of the information contained in and transmitted with this email by or to anyone other than the intended recipient or such recipient's authorized agent is unauthorized and strictly prohibited. If you have received this email in error, please notify the sender by email immediately and then delete it along with any attachments. Thank you.
More information about the Linux-PowerEdge