Bug 515742
| Summary: | RHEL5 cmirror tracker: openais ipc limits can lead to large cmirror problems | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 5 | Reporter: | Subhendu Ghosh <sghosh> |
| Component: | Documentation-cluster | Assignee: | Steven J. Levine <slevine> |
| Status: | CLOSED NOTABUG | QA Contact: | Content Services Development <ecs-dev-list> |
| Severity: | urgent | Docs Contact: | |
| Priority: | urgent | ||
| Version: | 5.4 | CC: | agk, ccaulfie, cluster-maint, dwysocha, edamato, ghelleks, heinzm, jbrassow, mbroz, pkennedy |
| Target Milestone: | rc | Keywords: | Documentation |
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | 514814 | Environment: | |
| Last Closed: | 2009-09-03 15:57:42 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Bug Depends On: | 514814 | ||
| Bug Blocks: | |||
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Comment 2
Steven J. Levine
2009-08-06 21:45:10 UTC
jbrassow: I'll be adding a note about this to the RHEL 5.4 version of the LVM manual, but I have two questions: 1. Am I correct that the default value for region size is set in the lvm.conf file? If so, is this worth mentioning -- that you can change the region size default there? 2. This note says that the user should increase the region size in the situation described to "something larger" than the default. Can we be more specific than "something larger"? The example sets the region size to 2 MB -- is that a generally recommended size (if we use it in the example it's probably what people will use)? Are there any guidelines here? -Steven I have added this information to the section in the LVM manuals on creating mirrored volumes. This is what the document says about region size:
--------------------
An LVM mirror divides the device being copied into regions that,
by default, are 512KB in size. You can use the -R argument of the lvcreate
command to specify the region size in MB. You can also change the default
region size by editing the mirror_region_size setting
in the lvm.conf file.
NOTE
Due to limitations in the cluster infrastructure, cluster mirrors greater than 1.5TB cannot be created with the default region size of 512KB. Users that require larger mirrors should increase the region size from its default to something larger. Failure to increase the region size will cause LVM creation to hang and may hang other LVM commands as well.
As a general guideline for specifying the region size for mirrors that are larger than 1.5TB, you could take your mirror size in terabytes and round up that number to the next power of 2, using that number as the -R argument to the lvcreate command. For example, if your mirror size is 1.5TB, you could specify -R 2. If your mirror size is 3TB, you could specify <command>-R 4</command>. For a mirror size of 5TB, you could specify -R 8.
The following command creates a mirrored logical volume with a region size of 2MB:
lvcreate -m1 -L 2T -R 2 -n mirror vol_group
With the release of RHEL 5.4 I'm closing this bug. |