Hi bu manzhao,
Thank for you quick response. I have some further queries to your answer
(wirtten with <sridhar> tag). It would be great if you could provide inputs for
them to understand ZFS better.
ZFS is base in storage pool, and a pool is consist of some vdevs in tree
structure. There is only one root vdev for each pool, and any number of vdevs
as the root's children.
<sridhar> 1. What exactly a Pool represents?. Let say I have a workstation
with a single hard disk of a size 100Gb. If I create a zpool and then a zfs how
the relation between these tow are shown with vdev ( the picture provided on
ondiskformat pdf).
2. Since ZFS can have multiple pools and each pool is having its own "root
vdev" then how "root vdev"s are interlinked and how ZFS maintains "root vdev"
list and where exctly?
Top-level vdev can be logical vdev or physical vdev. If a top-level vdev is a
logical vdev, it's type can be mirror or raidz and so on, except disk. And if
the top-level vdev is a mirror, then it can be consist of two or more device. A
top-level vdev also can be a physical vdev and linked to the root vdev directly.
<sridhar> Thank you for the explanation. Now i have a better understanding
towards Top-levev vdev and physical vdev.
A pool can be represented as a nvlist in implementation. A nvlist is a list
of a vdev's properties, and each property of vdev organizes as name/value pair,
like (name, value). Two key properties of the tree structure are vdev_tree and
chlidren. Nvlist and nvpair are all data structure which you can find in soure
browser, they define as nvlist_t and nvpair_t namely.
<sridhar> If ZFS on a machine is having multiple pools (i.e multiple root
vdevs) how it will be inter related?.
For more information about vdev and tree structure, you can see the ZFS
On-disk format in
http://www.opensolaris.org/os/community/zfs/docs/ondiskformat0822.pdf
<sridhar> Thank you for providing the link. I am trying to understand the
layout form the same pdf only.
Thanks & Regards,
sridhar.
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