D-Link DSN-3400-10 User's Manual for DSN-3200-10 Valid for firmware 1.6.1 - Page 88

Table 5-13 Modify System TCP/IP Settings Dialog Box Settings Setting Max Segment Size Window Scale TCP Timestamp Enabled Time to Live (TTL) PMTU Enabled Upper Layer Count Reset Description Indicates the maximum size TCP segment that can be accepted on a TCP/IP connection when the connection is established. Lets you use large windows during TCP/IP connections. On fast, high-bandwidth networks, a large TCP window provides greater efficiency by allowing for a greater amount of unacknowledged data. Causes the receiving computer to send a time-stamp reply back to the originating computer. Systems can use time-stamp requests and replies to measure the transmission speed of datagrams on a network. Specifies the default time to live (TTL) value for IP packets generated by the Windows TCP/IP stack. Lets the xStack Storage Array automatically adapt its packet size. Disabling this option forces the system to keep its default packet size (576 bytes), even when it receives an ICMP request to change its packet size; this can render some remote systems unreachable, because if intermediate systems on the path to the remote system cannot support the default packet size, the xStack Storage Array ignores their requests to make the packets smaller. Resets the TCP/IP upper layer counters. Resetting the counters simplifies the ability to look at the counters for an accurate percentage of packets sent or received. 5.4.11 Setting the Spare Count A spare is a drive that is present in the system (in the Available Pool) that cannot be used for any reason, except to rebuild space used by a volume on a failed drive. If a drive fails, the xStack Storage Array tries to find a replacement extent for every extent on that failed drive that was part of a redundant volume. First, a replacement extent is sought on a drive in the volume's pool (currently, the Blade A Base Pool). If space is not found in that pool and a drive exists in the Available Pool, one drive is obtained from the Available Pool and an extent is selected from that drive. In either case, a rebuild task starts to rebuild the volume's extent. If the available pool is empty, some volumes may not be rebuilt. The spare count exists to reduce that likelihood. The spare count default is 0, which means that no drives are kept in reserve for use in rebuilding extents (i.e., all drives can be obtained from the Available Pool for any purpose). Automatic Volume Creation, for example, takes drives from the Available Pool automatically as needed to satisfy the parameters in the request. If the spare count is set to a non-zero value, that number of drives is retained in the Available Pool for use only for rebuilds (i.e., operations other than rebuild cannot take a drive from the Available Pool if taking that drive results in the Available Pool having fewer drives than the spare count value). For example, assume that the spare count is one in an enclosure with 12 drives installed. If the administrator tried to perform an Automatic Volume Creation with both sliders at 10 (their maximum values), the volume is created using 11 drives, without touching the twelfth. If a drive fails, the twelfth drive moves automatically from the Available Pool to the volume's pool, so its space can be used to rebuild the original failed extent. 1. Click the xStack Storage icon on the Physical Resources tab. 2. Perform one of the following steps: - On the File menu, click Set Spare Count. 88 Chapter 5 Configuring the xStack Storage Array