From: Adam Megacz Date: Sat, 23 Jun 2007 18:07:03 +0000 (+0000) Subject: none X-Git-Url: http://git.openafs.org/?p=openafs-wiki.git;a=commitdiff_plain;h=c4f8b508a86495296fd51bc469e53c1e737f6992 none --- diff --git a/AFSLore/AdminFAQ.mdwn b/AFSLore/AdminFAQ.mdwn index c1ef534..7de4476 100644 --- a/AFSLore/AdminFAQ.mdwn +++ b/AFSLore/AdminFAQ.mdwn @@ -55,6 +55,10 @@ The Administration Section of the [[AFSFrequentlyAskedQuestions]].
  • 3.44 I get error message trhough syslogd: "afs: Tokens for user of AFS id 0 for cell foo.bar.baz are discarded (rxkad error=19270407)"
  • 3.45 I get tickets and tokens, but still get Permission denied.
  • 3.46 Recovering broken afs cache on clients
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  • 3.47 What does it mean for a volume to not be in the VLDB?
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  • 3.48 What is a Volume Group?
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  • 3.49 What is a Clone?
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  • 3.50 What is a Shadow?
    • @@ -1114,3 +1118,33 @@ Answer: /usr/afs/etc/UserList accepts only krb4 syntax. Use `joe.admin` instead [ other ls results as usual ] Flushing a particular file had no effect (the same error as shown above appears). Flushvolume took a long time, but when it eventually completed, the ls -la behaved exactly as one would expect. + +### 3.47 What does it mean for a volume to not be in the VLDB? + +If a volume is not in the VLDB, you will be unable to perform operations on it using its name; all "vos" operations will need to be done using its numerical id, server, and partition. Furthermore, if a volume is not in the VLDB, it cannot be reached via mountpoints. + +### 3.48 What is a Volume Group? + +A volume group is a set of volumes whose volume id numbers differ only in the last three bits. This means that up to eight volumes may belong to a single volume group. + +Volumes which share storage on a partition (for example, a volume and its backup, or the r/w and r/o copy of a volume on the same partition) must be part of the same volume group. + +### 3.49 What is a Clone? + +A clone of a volume is a read-only copy of that volume which shares on-disk storage with the original volume. Backup volumes are a particular kind of clone volume. Read-only replicas which reside on the same partition as their read-write volume are another particular kind of clone volume. In some other storage systems this kind of volume is called a "snapshot". + +Clone volumes must belong to the same volume group (see previous question) as the volume which they are a clone of. + +In addition to backup and readonly clones, you may create up to three additional clones of a volume. To do this, use "vos clone". + +When you "vos remove" a volume, its "backup" clone will also be removed automatically. However, clones created with "vos clone" are **not** removed automatically. Unfortunately, these "dangling clones" will no longer be in the VLDB (see question 3.47). + +### 3.50 What is a Shadow? + +A shadow of a volume is a duplicate of that volume which resides on a different partition. Shadow volumes do not share storage with their original volumes (unlike clones). A readonly volume on a **different** partition than its readwrite volume could be considered one particular example of a shadow volume; however, in practice the term "shadow volume" is used to refer to volumes created with "vos shadow" and not to refer to readonly volumes. + +A shadow of any readwrite volume may be created using the "vos shadow" command. This will create a new volume which is a shadow of the original volume, and will copy the contents of the old volume to the new volume. This will also set a bit in the header of the new shadow volume that identifies it as a shadow volume. Shadow volumes do not appear in the VLDB (see question 3.47) + +You can "refresh" a shadow volume from its original with "vos shadow -incremental". This operation will first check to make sure that the target of the operation is a shadow volume, to prevent the administrator from accidentally corrupting a non-shadow volume. However, if you shadow from a readwrite volume to some shadow of **another** volume, the shadow will be corrupted and will have to be deleted. Vos shadow will only copy data which has changed, so it is very efficient. + +You can remove the shadow bit from a volume's header with "vos shadow -live". This will remove the shadow bit and create a VLDB entry for the volume.