OpenStack Object Storage (swift)

Give me more details about Glance and Swift

Asked by DzungVuAnh

Hi Everyone!
I saw your recommendation in community, I know you are the people who can help me understand more about Openstack. If possible, please describe for me something what I feel confusing.

First of all, I want to ask you about the glance. I used the command "glance add name="TestSwift1" distro="Test1" is_public=true </root/file names" to add image and transfer data from Cloud Controler Server to Swift Proxy Server for backing up. Because that data will have 3 extra copies in Swift and then how can I get back the transfer data with glance? What commnad should I use to get the transfer data back?

Secondly, I want to know what happend If I have some different Storage node. The first one = 100 GB, second one = 250GB, last one = 500GB. What is the maximum of transfer data could be received in Swift? 100GB or 850GB? and what happend if I send the transfer data more than 100 GB or more than 250GB to the Swift?

Please give me some advise, thanks in advance!

sincerely yours,

Dzung Vu Anh

Tel: +84.904800904
Email: <email address hidden> - <email address hidden>
R&D Department - Viettel Software Center - Viettel Corporation

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Marcelo Martins (btorch) said : 		#1

Hi DzungVuAnh,

You should direct the Glance question(s) to https://launchpad.net/glance since they will be able to explain glance better and in more detail.

In regards to swift, you should always have each storage node with the same amount of storage during an initial deployment.

Ok, the data is stored 3 times, so if you send a file greater than 100GB (say 120GB) it will fail since the storage node with only 100GB available will run out of space.

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DzungVuAnh (anhdungcha) said : 		#2

Hi Marcelo Martins and all U guys!

I received formation from some people and they so differerent. I highly appreciate your all comments. You and some people tell me about the limited of small disk drive in cluster. Based on your comment, if first storage node = 100GB, second storage node = 250 GB, third storage node = 500GB, then I send 120GB to Swift and get failed when the first storage node full.
--> It means Swift Architecture doesn't have mechanism to change the location when one or more than one disk run out of space.

Another information is that Swift doesn't care about the drive disk you have, Swift just care about the total space of disk drive.
--> It means, If you have thousands disk drive and sorted by the number from 1 to n, then you transfer data to Swift. If the 1st drive full, Swift will take the rest of data to another location.

So, I am really confusing, Do u have any document or tutorial mention about that information, please give it to me.

Thanks in advance and looking forward to hearing some good news from U.

sincerely yours,

Dzung Vu Anh

Tel: +84.904800904
Email: <email address hidden> - <email address hidden>
R&D Department - Viettel Software Center - Viettel Corporation

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Mike Barton (redbo) said : 		#3

I don't think this is exactly written anywhere, so I'll try to explain.

Swift makes multiple copies of your data (usually 3 copies) and puts
them on separate drives. That's so if one drive blows up, you still
have the other copies. But if you only have 3 drives, once the
smallest drive gets full, there's nowhere to put a third copy and the
whole thing is effectively full.

This problem disappears pretty quickly when you add more drives. And
swift is good at figuring out the best way to use the drives you have.

(actually, this behavior describes zones better than drives, but I'm
assuming each of your drives is in its own zone right now)

The way to handle different size disks is to give them different
weights when building the ring. You could use the number of GB in the
drive as the weight or something, I think they just have to be
proportionally correct.

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