My daily readings 07/13/2009

  • tags: lvm, snapshot

    • Number of customers have reported the LVM gives very high penalty when snapshots are enabled (leave along if you try to run backup at this time) and so I decided to look into it.
    • The performance without LVM snapshot was 159 io/sec which is quite expected for single thread and no BBU. With LVM snapshot enabled the performance was 25 io/sec which is about 6 times lower !
  • tags: no_tag

    • This tutorial shows how you can create backups of LVM partitions with an LVM feature called LVM snapshots. An LVM snapshot is an exact copy of an LVM partition that has all the data from the LVM volume from the time the snapshot was created. The big advantage of LVM snapshots is that they can be used to greatly reduce the amount of time that your services/databases are down during backups because a snapshot is usually created in fractions of a second. After the snapshot has been created, you can back up the snapshot while your services and databases are in normal operation.
  • tags: no_tag

    •  但是由于其PV->VG-LV三层架构的存在,在后期数据迁移和恢复上比较复杂

        例如,当前磁盘使用了/dev/VolGroup00/LogVol01这样的名称

        把这块磁盘挂载到其他服务器上后,如果存在另外一块硬盘名称也是由LVM管理

        并且默认也使用了“/dev/VolGroup00/LogVol01”的名称

        那么两个硬盘的VG名称冲突,就无法继续挂载LV读取数据了

        这种冲突,在两个硬盘都是数据磁盘的时候,还可以修改名称来解决

        但是,如果冲突双方中的一块是系统硬盘,那么则LVM拒绝对磁盘做卸载、改名等处理

        此时第二块硬盘里边的数据就恢复不出来了

    • 因此,在服务器上,为了保证尽可能好的后期灾难恢复,不推荐用LVM

        最好使用简单直接使用磁盘分区格式化,以便恢复数据

        如果非要用LVM,请注意,在安装系统分区之初,就给自己磁盘的LVM起一个不容易冲突的唯一的名字

        例如/dev/VolHehe001、/dev/VolHehe002等

  • tags: lvm

  • tags: RAID-1

    • When one of the disks in the RAID set fails, the other one continues to function. When the failed disk is replaced, the data is automatically cloned to the new disk from the surviving disk. RAID 1 also offers the possibility of using a hot standby spare disk that will be automatically cloned in the event of a disk failure on any of the primary RAID devices.

      RAID 1 offers data redundancy, without the speed advantages of RAID 0. A disadvantage of software-based RAID 1 is that the server has to send data twice to be written to each of the mirror disks. This can saturate data busses and CPU use. With a hardware-based solution, the server CPU sends the data to the RAID disk controller once, and the disk controller then duplicates the data to the mirror disks. This makes RAID-capable disk controllers the preferred solution when implementing RAID 1.

  • tags: PDF

  • tags: freemium

Posted from Diigo. The rest of my favorite links are here.

2 Responses to “My daily readings 07/13/2009”

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