Talking about Exchange Server mail storage System

After learning how and how the Exchange Server store works, let's look at some management tips for the messaging storage System. After mastering the principle of the administrator will have a deeper understanding of these skills, in the actual work to be confident and comfortable.

Selection and design of software and hardware for Exchange storage systems

Let's first look at how to select the appropriate disk hardware for the database files and log files for Exchange server.

Based on the log file's role in restoring the database as described in the previous installment, we learned that when the database is corrupted, you can restore the database to a state prior to the problem by restoring the backup on tape and leveraging the existing log files on the system. Therefore, database files and log files need to be stored on separate physical disks to prevent disk hardware failure causing both database and log corruption. Microsoft's documentation clearly states that, under the premise of a valid backup, either the database or log is damaged and can be recovered. However, if the database and log are damaged at the same time, you can only restore the backup to the state of the backup time by restoring it.

Typically, an important server storage system in an enterprise uses a RAID array that is implemented through a hardware system. The common RAID systems are RAID 5 and RAID 1. The characteristics of these two systems are as follows:

RAID 5: Writes data to the disk in the array, and the parity data is stored on each disk in the array, allowing for a single disk error. RAID 5 is also a data parity to ensure data security, but it is not a separate hard disk to store data parity bit, but to the data section of the check bit interaction on each hard disk. If any one of the hard drives is damaged, the corrupted data can be rebuilt according to the parity bit on the other hard disk. The utilization of the hard disk is (n-1/n)%.

RAID1 the disk array's hard disk into the same two groups, mirroring each other, when any disk media failure, you can use the data recovery on its mirror, thereby improving the system's fault tolerance. The operation of the data is still divided into parallel transmission mode. So RAID 1 not only improves read and write speed, but also strengthens the reliability of the system. But its disadvantage is the low utilization of hard disk, redundancy of 50%.

From the above features, RAID 5 is biased towards data security; RAID 1 (mirrored disk) emphasizes read-write speed, provided that the data is secure.

Microsoft's recommended Exchange store system storage hardware requirements.

From this we can see that the database files (EDB files and STM files) are placed on the RAID 5 system; Log files are stored using a RAID 1 strategy for each storage group.

Microsoft's design is designed to improve the performance of the Exchange store. For database files, these files are often very large in size and need to be read and written very frequently during day-to-day operations. From a security standpoint, database files are much more important than log files. Therefore, the use of a RAID 5 system to save data files, you can maximize the security of the file data: In the frequent reading and writing, through the check bit to ensure that the data will not be wrong, when the disk hardware failure occurs, can make the system unaffected.

For log files, readers should first recall the role of the log file we talked about in the previous issue: making in-memory transactions written to the hard disk as quickly as possible. The exchange's log file, which is not recovered from the backup tape, will only be written once and read once in a lifetime. When written, Exchange Server writes the data in memory to a log file in 5MB, which occurs when Exchange Server writes the contents of the log to the database. Therefore, we can find that for the disk system that holds the log file, its read and write pressure is not very large, but requires a very fast write speed. The very fast write speed is guaranteed by two points: first, a RAID 1 system with a faster write speed (as opposed to RAID 5, which saves a lot of time); second, each storage group exclusively has a RAID 1 system (both the raid The 1 array is used only to hold the log files of the specific storage group, so we reduce the number of fragments on the disk to the minimum. Ideally, each sector of the log file is next to each other, and when the disk writes data, it does not need to reposition the head because of disk fragmentation, which maximizes the performance of the write.