From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: Checking the sanity of SATA disks Date: Mon, 07 Nov 2005 14:22:07 -0500 Message-ID: <436FA95F.4030007@tmr.com> References: <20051004142913.GK6594@strugglers.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20051004142913.GK6594@strugglers.net> Sender: linux-raid-owner@vger.kernel.org To: Andy Smith Cc: linux-raid List-Id: linux-raid.ids Andy Smith wrote: >Hello, > >I have a home fileserver with 4 SATA disks in a RAID 5. As I am >sure you are aware, SATA devices in Linux currently cannot be >queried for SMART info, so I can't do SMART health checks of these >devices. > >Also there is still the tendency for Linux Software RAID to kick >devices out of the array as soon as there is any error on them. > >I really don't want to be in the situation where a drive dies, I fit >a new one, and during the resync another device is kicked out >because of spontaneously finding a bad sector. > >I tried simply doing a > > dd if=/dev/sd[abcd] of=/dev/null > >To check each disk in a very unsubtle fashion, but it drives the >load average on the machine way way up (like to 20+) and makes it >very unresponsive (wait several minutes for a keypress to be >acknowledged), even if I run it under nice -n 19. > You (a) want to use larger buffers, and (b) a program which uses O_DIRECT for i/o. I had a news server which was running 28 aps until I started using dd, then it dropped to 3 aps. Usinf O_DIRECT there is no measurable slowdown (and no buffer contention). -- bill davidsen CTO TMR Associates, Inc Doing interesting things with small computers since 1979