Bug 151652
| Summary: | anaconda rejects single-member raid 1 | ||
|---|---|---|---|
| Product: | [Fedora] Fedora | Reporter: | Alexandre Oliva <oliva> |
| Component: | anaconda | Assignee: | Alexandre Oliva <oliva> |
| Status: | CLOSED WONTFIX | QA Contact: | Mike McLean <mikem> |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | 4 | CC: | dledford, wtogami |
| Target Milestone: | --- | ||
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2005-05-13 18:46:36 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: | |||
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Description
Alexandre Oliva
2005-03-21 14:25:31 UTC
We're just not going to support single-device mirrors. Care to justify in public why you make such a distinction between the following two scenarios: 1) box with 2 disks is assigned to be a server. System manager decides they want to tolerate 2 disk failures, so one more disk is ordered. Meanwhile, system manager goes ahead and installs the box with 2-member raid1 devices, and starts configuring the server. When the new disk arrives, the future server is brought down, the disk is added, partitioned like the 2 existing disks, mdadm --grow is used to make the 2-member arrays 3-member arrays, and mdadm --add adds the partitions in the new disk to the running arrays 2) box with 1 disk is assigned to be a server. System manager decides they want to tolerate 1 disk failure, so one more disk is ordered. Meanwhile, system manager goes ahead and installs the box with 1-member raid1 devices, and starts configuring the server. When the new disk arrives, the future server is brought down, the disk is added, partitioned like the 1 existing disk, mdadm --grow is used to make the 1-member arrays 2-member arrays, and mdadm --add adds the partitions in the new disk to the running arrays. Why is (1) supported, but (2) isn't? This is not a made-up scenario, it actually is happening to me right now. I can't install-test rawhide on one of my boxes because one of the disks died and the replacement will take a while to arrive. The number of people who have ever considered doing #2 is, as far as I can tell, 1. The number of users who might try to do it accidentally were the code to allow it is significantly larger, and UI to tell them that it *might* be ok to do that is will result in a many more users doing this by accident, likely incurring extra load for support and development. Also, ignoring the completely abstract "why is 2->3 ok but 1->2 bad" argument, a one volume RAID mirror simply does not make sense. So, in short, the latter isn't supported because it doesn't gain us *anything*, whereas the former has a clear gain. Another reason to permit single-member raid devices: they can be partitioned. If you, for whatever reason, need more than 16 partitions on a SCSI disk, you can create multiple single-member partitionable raid[01] devices as partitions in the actual disk, and then create partitions in them. If you need to do that, you should be using LVM instead. LVM would go atop of the smallish partitions. Reason being that having smaller bits of disk to manage enables you to move stuff around to e.g. change raid levels without requiring twice the disk space. Which happens to be the exact reason to want more than 15 partitions in the first place. |