Dell DX6004S DX Object Storage Release Notes - Page 7

the bucket on one cluster and wait for the bucket to be replicated to the other cluster. Failure to do so results in objects contained in one bucket or the other being inaccessible. • Named object deletes. Deleting a named object does not decrement the stream count displayed at the top of the cluster status page on the Admin Console. • Use curl version 7.19.7 or later. If you use curl with DX Storage, and you use the new authorization feature, you must use curl version 7.19.7. There are known issues with earlier curl versions. • Last-Modified Header with Previous DX Storage Versions The Last-Modified header is not currently returned for streams written with DX Storage versions earlier than 4.0. New streams and anchor stream updates written with 4.0 or later do contain the header. • Vol Number on Admin Console The Vol # labels next to each DX Storage node in the Admin Console are listed in arbitrary order. The Admin Console labels do not correspond to physical drive slots in the machine chassis. However, the volume names do match the physical drives in the machine chassis. • Consumer-Grade Disk Drives. Some non-enterprise-class disk drives have lengthy error recovery logic. When an error occurs on these types of drives, it might take minutes for a disk read or write operation to complete. In these cases, the client could see very long response times, or it might even see a socket timeout if the delay is too long. Many enterprise or server grade disks are designed to return errors within a limited period of time, allowing recovery or rebuild operations to begin immediately and to eliminate the lengthy delays on I/O operations. Dell recommends against the use of consumer grade disk drives and does not support them in a high demand environment. • Avoiding Client Timeouts with Large Streams. Client operations with large streams (1GB or larger) can take several seconds or more, depending on stream size. Clients that support large stream operations should set their socket timeouts accordingly to avoid client timeout errors. • Network Time Protocol. Dell strongly recommends you identify an NTP time source in at least one of your cluster or node configuration file, as discussed in the DX Object Storage Getting Started Guide. Without NTP, the individual clocks on the nodes of the cluster will still be synchronized to each other, but they will likely drift over time so that the cluster will have the wrong time. This will impact stream storage policies such as retention and replication as discussed in the following bullet. • Time Clock Synchronization. When formatting storage policies in lifepoint headers, it is very important that the local clock be reasonably accurate so the end dates of the lifepoints reflect the true UTC time. The DX Storage cluster itself can (and should) synchronize itself to an accurate time source as specified in the DX Storage Getting Started Guide. If the client mistakenly specifies the wrong end date in a stream's storage policy, perhaps because its local clock is set incorrectly, there could be unintended consequences, including premature deletion, when DX Storage enforces that policy. • Replica Terminology. The term replica has special meaning in the context of DX Storage. All instances of a stream stored within a DX Storage cluster are identical - there is no original. Therefore, saying there are two replicas of a stream means there are exactly two identical instances (not an original plus two copies). • Not Found Errors in a Busy Cluster. A READ, INFO, UPDATE, or DELETE request to a heavily loaded cluster might rarely result in a 404 Not Found response, even if the requested object is Copyright © 2010 Caringo, Inc. All rights reserved 4 Version 5.0 December 2010