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Zookeeper >> mail # dev >> help! some questions about zk


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Re: help! some questions about zk
Hopefully this should only hurt availability/liveness, not cause you
to loose data.
ZooKeeper will not allow you to issue any more updates before having
again at least 3 servers.
This of course assumes that servers still have the information they
previously wrote to disk after they reboot.
On Mon, Oct 21, 2013 at 4:53 PM, Thawan Kooburat <[EMAIL PROTECTED]> wrote:
> (2) You can lose a committed data if have more failure than what the
> quorum is configured to support (eg. losing 3 out of 5 hosts)
>
> --
> Thawan Kooburat
>
>
>
>
>
> On 10/21/13 4:48 PM, "Alexander Shraer" <[EMAIL PROTECTED]> wrote:
>
>>Hi,
>>
>>(1) Zab is an atomic broadcast protocol, it satisfies strong ordering
>>properties. Check out the paper:
>>http://www.stanford.edu/class/cs347/reading/zab.pdf
>>
>>Its used to propagate updates in the same order to all the ZooKeeper
>>servers. The provided consistency in ZooKeeper is basically sequential
>>consistency +
>>real-time-order on writes. This is strong, although not linearizable
>>(its possible that you read from a server that has stale data).
>>
>>If you use the sync call before a read, ZooKeeper provides
>>ilnearizability for sync+read and write operations (this is true with
>>certain timing assumption made in ZooKeeper for efficiency).
>>
>>(2) No, only a suffix of uncommitted operations can disappear.
>>Operations acked by a quorum never dissappear.
>>
>>(3) For read operations the server responds immediately using local
>>state. For writes it responds after a quorum acked the update.
>>
>>
>>Alex
>>
>>On Mon, Oct 21, 2013 at 1:47 AM, 聂安 <[EMAIL PROTECTED]> wrote:
>>> hi all,
>>>
>>> About zk, I got some questions bothered me for one week, which can be
>>>described as follows:
>>>
>>> (1)  Does zab guarantee a strong consistency?
>>>
>>> (2) Could those committed proposals on new-elected-followers be deleted
>>>when initially synced?
>>>
>>> (3)  When does the server in zk respond to the client? After commiting
>>>the proposal?
>>>
>>> thank you!
>>>
>>>
>>>
>>>
>>> Regards,
>>>
>>> An.Nie
>