Effect of enclosure unavailability

Content Platform S Series Node Help

Version
4.0.0
Audience
anonymous
Part Number
MK-HCPS027-02

When storing the data for an object, the S Series Node spreads the selection of drives for the data and parity chunks across the available enclosures. If the S Series Node has five or more available enclosures (S31 Nodes) or six or more available enclosures (S32 Nodes) and the chunks are distributed optimally across the enclosures, no enclosure will have more than six chunks for the object. In this case, any one of those enclosures, except the base enclosure, can become unavailable without affecting the ability of the S Series Node to reconstruct the object data.

If the S Series Node has fewer than five enclosures (S31 Nodes) or six enclosures (S32 Nodes), one enclosure will have more than six chunks for the object. If that enclosure becomes unavailable and the S Series Node cannot access the drives in the enclosure, the object becomes irreparable and remains so until the enclosure becomes available again.

For example, if an S31 Node has four enclosures, three of the enclosures will have six chunks each for the object being stored, and the fourth enclosure will have eight chunks. If the enclosure with eight chunks becomes unavailable and the drives in the enclosure are inaccessible, the object becomes irreparable because only 18 chunks for the object are accessible.

With four enclosures, if one enclosure becomes unavailable and the drives on the enclosure are inaccessible, approximately one-quarter of the objects stored on the S Series Node become irreparable. With three enclosures, if one enclosure becomes unavailable and the drives on the enclosure are inaccessible, approximately one-third of the objects stored on the S Series Node become irreparable.