Bug 1413106
Summary: | full snapshot check on bootup: bootup duraction increases with increased changed blocks | ||
---|---|---|---|
Product: | [Community] LVM and device-mapper | Reporter: | Gerben <gerbgeus> |
Component: | lvm2 | Assignee: | LVM and device-mapper development team <lvm-team> |
lvm2 sub component: | Snapshots | QA Contact: | cluster-qe <cluster-qe> |
Status: | CLOSED NOTABUG | Docs Contact: | |
Severity: | unspecified | ||
Priority: | unspecified | CC: | agk, heinzm, jbrassow, msnitzer, prajnoha, zkabelac |
Version: | 2.02.133 | Flags: | rule-engine:
lvm-technical-solution?
rule-engine: lvm-test-coverage? |
Target Milestone: | --- | ||
Target Release: | --- | ||
Hardware: | Unspecified | ||
OS: | Unspecified | ||
Whiteboard: | |||
Fixed In Version: | Doc Type: | If docs needed, set a value | |
Doc Text: | Story Points: | --- | |
Clone Of: | Environment: | ||
Last Closed: | 2017-01-14 09:41:51 UTC | Type: | Bug |
Regression: | --- | Mount Type: | --- |
Documentation: | --- | CRM: | |
Verified Versions: | Category: | --- | |
oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
Cloudforms Team: | --- | Target Upstream Version: | |
Embargoed: |
Description
Gerben
2017-01-13 16:10:22 UTC
The short answer could be: Do not use old snapshots with large COW volumes. Switch to thin-provisioning which is simply way better. The longer answer is - old snapshot was meant to be used for temporarily used consistent filesystem snapshots when taking their backups. Who ever came with the idea of using this for multi-GB snapshot and keep them 'permanent' (long period of time) misunderstood the original purpose. Old snapshot simply can't deliver as the metadata are thrown across whole COW volume which effectively means you have to read (& parse) full COW volume size. It also does occupy a lot of RAM then... The old format is unfixable and very inefficient when taking more snapshost (although in newer kernels there were some patches trying to speed-up disk read performance) New format is called thin-provisioning - so please use this one. Hi, Yes: thin-provisioning does show proper performance characteristics. From what I've read about it it also has nice characteristics on multiple (incremental) snapshots on the same source LV. Defining thin-provisioning looks easy as well, just an extra layer of LV from which the final LV's are defined. When creating snapshots on thin provisioned LV: do NOT provide the size parameter or the snapshot will end up outside the thin provisioning completely. LVM2 keeps surprising me time and time again: nice!! Gerben |