From mboxrd@z Thu Jan 1 00:00:00 1970 From: joystick Subject: Using SCSI timeouts in place of ERC Date: Mon, 20 Aug 2012 13:37:00 +0200 Message-ID: <5032215C.9080105@shiftmail.org> Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Sender: linux-scsi-owner@vger.kernel.org To: linux-raid , linux-scsi List-Id: linux-raid.ids Hello lists I am wondering what kind of support I can get from linux for "inexpensive" (SATA over SAS HBA in my case) disks on RAID ... Inexpensive non-raid-edition disks haven't got settable ERC timeout (scterc) and can take very long time to respond in case of unreadable sector However I see an /dev/sdX/device/timeout tunable Supposing that I accept one disk being dropped from the array at the first unreadable sector, can I set that tunable low such as 10sec and live happy? Unfortunately I have read that the expiration of the SCSI timeout can trigger a "Host" reset in case the drive does not respond to a reset message https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/5/html/Online_Storage_Reconfiguration_Guide/task_controlling-scsi-command-timer-onlining-devices.html would that drop all my drives from the array? That would be a major problem. Firstly, in "reset the bus": isn't the bus just an electrical wire? How can it be "reset" and what does that do? I can understand in the case of iSCSI the bus is maybe the TCP socket, I can somehow understand that it can be reset, but what about physically attached disks? I suppose "device" is the disk.. ok for that one, suppose it's doomed I suppose "host" is the HBA card... so what does a reset of the HBA do? Does it drop all the drives and rescan? MD wouldn't react well *at all* to this Thank you J