flyinweb's blog

这几天格式化硬盘，记录一下用到的命令：

[root@db ~]# fdisk /dev/sdb

The number of cylinders for this disk is set to 253981.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)

Command (m for help): p

Disk /dev/sdb: 2089.0 GB, 2089072092672 bytes
255 heads, 63 sectors/track, 253981 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdb1 1 124495 1000006056 83 Linux

Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 2
First cylinder (124496-253981, default 124496):
Using default value 124496
Last cylinder or +size or +sizeM or +sizeK (124496-253981, default 253981):
Using default value 253981

Command (m for help): p

Disk /dev/sdb: 2089.0 GB, 2089072092672 bytes
255 heads, 63 sectors/track, 253981 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdb1 1 124495 1000006056 83 Linux
/dev/sdb2 124496 253981 1040096295 83 Linux

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table.
The new table will be used at the next reboot.
Syncing disks.

此时，分区里看不到新建的磁盘分区，提示通过重启才可以重用分区表，此时可以通过partprobe探测硬盘：

背景：6块硬盘，每个1TB，用一块硬盘做raid0,安装系统，剩余5块做raid5。由于ext3文件系统不支持大于2TB的分区，所以考虑使用GPT首先以root身份登录系统，查看硬盘信息：fdisk -l
[root@libftp ~]# fdisk -l

Disk /dev/cciss/c0d0: 1000.1 GB, 1000171331584 bytes
255 heads, 63 sectors/track, 121597 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/cciss/c0d0p1 * 1 33 265041 83 Linux
/dev/cciss/c0d0p2 34 116105 932348340 83 Linux
/dev/cciss/c0d0p3 116106 118655 20482875 83 Linux
/dev/cciss/c0d0p4 118656 121597 23631615 5 Extended
/dev/cciss/c0d0p5 118656 120567 15358108+ 83 Linux
/dev/cciss/c0d0p6 120568 121587 8193118+ 82 Linux swap / Solaris

WARNING: GPT (GUID Partition Table) detected on '/dev/cciss/c0d1'! The util fdisk doesn't support GPT. Use GNU Parted.

Disk /dev/cciss/c0d1: 4000.6 GB, 4000684662784 bytes
255 heads, 63 sectors/track, 486388 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/cciss/c0d1p1 1 267350 2147483647+ ee EFI GPT

1、安装
首先要在存储设备上做好RAID，设置好iSCSI 目标方（target）。
这里主要说明iSCSI initiator的安装。
不同的操作系统对应各自的iSCSI initiator，以Redhat enterprise5为例。到网上下载iscsi-initiator-utils-6.2.0.742-0.5.el5.i386.rpm
# rpm -ivh iscsi-initiator-utils-6.2.0.742-0.5.el5.i386.rpm
在服务器上安装了iSCSI initiator以及iscsiadm
iscsiadm是基于命令行的iscsi管理工具，提供了对iscsi节点、会话、连接以及发现记录的操作。
iscsiadm的使用说明可以查看/usr/share/doc/iscsi-initiator-utils-6.2.0.742/README，也可以运行man iscsiadm或iscsiadm -help

ZooKeeper is a high-performance coordination service for distributed applications. It exposes common services - such as naming, configuration management, synchronization, and group services - in a simple interface so you don't have to write them from scratch. You can use it off-the-shelf to implement consensus, group management, leader election, and presence protocols. And you can build on it for your own, specific needs.

This information is available in many many other places, however I am putting it on here because I know it will be here for me to refer to. Also it is handy, as I know I can access my web-site even if the MTU is misconfigured.

For some reason that has escaped me Path MTU Discovery in Windows just doesn’t seem to figure out the MTU for a given path (something to do with routers being poorly configured to not respond to ICMP requests). So Windows uses the default. For the most part this doesn’t affect anyone, however if it dos affect you, it really annoys you. Failure of PMTUD will result in some websites not loading correctly, having trouble connecting to normally reliable online services and general Internet weirdness.