[openstack-dev] Proposal for dd disk i/o performance blueprint of cinder.

CARVER, PAUL pc2929 at att.com
Thu Jan 16 13:21:24 UTC 2014

Alan Kavanagh wrote: 

>I posted a query to Ironic which is related to this discussion. My thinking was I want to ensure the case you note here (1) " a >tenant can not read another tenants disk......" the next (2) was where in Ironic you provision a baremetal server that has an >onboard dish as part of the blade provisioned to a given tenant-A. then when tenant-A finishes his baremetal blade lease and >that blade comes back into the pool and tenant-B comes along, I was asking what open source tools guarantee data destruction >so that no ghost images  or file retrieval is possible?

That is an excellent point. I think the needs of Ironic may be different from Cinder. As a volume manager Cinder isn't actually putting the raw disk under the control of a tenant. If it can be assured that (as is the case with NetApp and other storage vendor hardware) that a "fake" all zeros is returned on a read-before-first-write of a chunk of disk space then that's sufficient to address the case of some curious ne'er-do-well allocating volumes purely for the purpose of reading them to see what's left on them.

But with bare metal the whole physical disk is at the mercy of the tenant so you're right that it must be ensured that the none of the previous tenant's bits are left lying around to be snooped on.

But I still think an *option* of wipe=none may be desirable because a cautious client might well take it into their own hands to wipe the disk before releasing it (and perhaps encrypt as well). In which case always doing an additional wipe is going to be more disk I/O for no real benefit.

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