From 614d448e30ade178a9e2e8d2d66625cfc5b208e6 Mon Sep 17 00:00:00 2001 From: Richard Henwood Date: Wed, 18 May 2011 09:49:10 -0500 Subject: [PATCH] FIX: xrefs --- ManagingFailover.xml | 51 +++++++++++++-------------------------------------- 1 file changed, 13 insertions(+), 38 deletions(-) diff --git a/ManagingFailover.xml b/ManagingFailover.xml index 59e0077..41b0e99 100644 --- a/ManagingFailover.xml +++ b/ManagingFailover.xml @@ -1,30 +1,19 @@ - + - Managing Failover + Managing Failover - This chapter describes failover in a Lustre system and includes the following sections: + This chapter describes failover in a Lustre system and includes the following sections: + - Lustre Failover and Multiple-Mount Protection - - - + - - - - - - Note -For information about high availability(HA) management software, see the Lustre wiki topic Using Red Hat Cluster Manager with Lustre or the Lustre wiki topic Using Pacemaker with Lustre. - - - - -
- <anchor xml:id="dbdoclet.50438213_pgfId-1292319" xreflabel=""/> -
- 20.1 <anchor xml:id="dbdoclet.50438213_13563" xreflabel=""/>Lustre Failover and <anchor xml:id="dbdoclet.50438213_marker-1301522" xreflabel=""/>Multiple-Mount Protection + + For information about high availability(HA) management software, see the Lustre wiki topic Using Red Hat Cluster Manager with Lustre or the Lustre wiki topic Using Pacemaker with Lustre. + +
+ 20.1 Lustre Failover and <anchor xml:id="dbdoclet.50438213_marker-1301522" xreflabel=""/>Multiple-Mount Protection The failover functionality in Lustre is implemented with the multiple-mount protection (MMP) feature, which protects the file system from being mounted simultaneously to more than one node. This feature is important in a shared storage environment (for example, when a failover pair of OSTs share a partition). Lustre's backend file system, ldiskfs, supports the MMP mechanism. A block in the file system is updated by a kmmpd daemon at one second intervals, and a sequence number is written in this block. If the file system is cleanly unmounted, then a special "clean" sequence is written to this block. When mounting the file system, ldiskfs checks if the MMP block has a clean sequence or not. Even if the MMP block has a clean sequence, ldiskfs waits for some interval to guard against the following situations: @@ -32,26 +21,13 @@ If I/O traffic is heavy, it may take longer for the MMP block to be updated. - - - If another node is trying to mount the same file system, a "race" condition may occur. - - - With MMP enabled, mounting a clean file system takes at least 10 seconds. If the file system was not cleanly unmounted, then the file system mount may require additional time. - - - - - - Note -The MMP feature is only supported on Linux kernel versions >= 2.6.9. - - - - + + The MMP feature is only supported on Linux kernel versions >= 2.6.9. +
<anchor xml:id="dbdoclet.50438213_pgfId-1292355" xreflabel=""/>20.1.1 Working with Multiple-Mount Protection On a new Lustre file system, MMP is automatically enabled by mkfs.lustre at format time if failover is being used and the kernel and e2fsprogs version support it. On an existing file system, a Lustre administrator can manually enable MMP when the file system is unmounted. @@ -72,6 +48,5 @@ When MMP is enabled, if ldiskfs detects multiple mount attempts after the file system is mounted, it blocks these later mount attempts and reports the time when the MMP block was last updated, the node name, and the device name of the node where the file system is currently mounted.
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