Exchange Server email storage system-Tips (1)

After learning about how Exchange Server Store works and its features, we will introduce some management skills for the mail storage system. After mastering the principles, the Administrator will have a deeper understanding of these skills and be confident and easy to use in practical work.
Selection and Design of Exchange storage system hardware and software
First, let's take a look at how to select the appropriate disk hardware for the database files and Log files of the Exchange Server.
According to the role of Log files on database recovery described in the previous article, we know that when the database is damaged, the backup on the tape is restored and the existing Log files of the system are used, you can restore the database to a status before a problem occurs. Therefore,Database files and log files must be stored on different physical disks.To prevent both database and log damages caused by disk hardware faults. Microsoft's document clearly states that, under the premise of a valid backup, any damage to the database or log can be recovered. However, if the database and log are damaged at the same time, you can only restore the backup to restore the State at the backup time.
Generally, important server storage systems in enterprises use RAID arrays implemented by hardware systems. Commonly used RAID systems include RAID 5 and RAID 1. The two systems have the following features:
RAID 5: write data to the disk in the array. The parity data is stored on each disk in the array. An error occurs on a single disk. RAID 5 also ensures data security by the Data check bit, but it does not store the data check bit on a separate hard disk, but stores the check bit of the Data Segment on each hard disk. In this way, damaged data can be rebuilt based on the check bit on other hard disks. Hard Disk utilization is n-1/n) %.
RAID1 divides the hard disks in the disk array into the same two groups and mirror each other. When any disk medium fails, the data on the image can be restored to improve the fault tolerance capability of the system. Data operations are still performed in parallel After partitioning. Therefore, RAID 1 not only improves read/write speed, but also enhances system reliability. However, the disadvantage is that the hard disk utilization is low, and the redundancy is 50%.
From the above features, RAID 5 focuses on data security; RAID 1 mirror disk) emphasizes read/write speed while ensuring data security.
Is the storage hardware requirement of the Exchange Store system recommended by Microsoft.
520) this. width = 520; "onclick = javascript: window. open (this. src); src = "/files/uploadimg/20051206/1011280 .gif" onload =" javascript: if (this. width> 520) this. width = 520; "align = absMiddle border = 0>
From this we can see that the database file edb and stm files are placed on the RAID 5 system. The Storage of Log files adopts a RAID 1 policy for each Storage Group.
Microsoft is designed to fully improve the performance of Exchange Store. For database files, the size of these files is usually very large and needs to be read and written frequently during daily operation. From the security perspective, the importance of database files is far greater than that of log files. Therefore, using the RAID 5 system to save data files can ensure the data security of files to the maximum extent: During frequent read/write operations, data can be checked in bits to avoid errors; when a disk hardware fault occurs, the system is not affected.
For log files, please remember the role of the log files we talked about in the previous period: To write transactions in the memory to the hard disk as soon as possible. Exchange log files are only written once and read once in a lifetime without recovering from the backup tape. At the time of writing, the Exchange Server writes data in the memory to a log file in the unit of 5 MB. At the time of reading, the Exchange Server writes the log content to the database. Therefore, we can find that for the disk system storing log files, the read/write pressure is not very high, but the write speed is very fast. The extremely fast write speed is guaranteed by two points: first, the RAID 1 system with a fast write speed does not need to calculate the check bit relative to RAID 5, which saves a lot of time); second, each Storage Group occupies a RAID 1 system. This RAID 1 array is used only to save log files of a specific Storage Group, we can minimize the number of fragments on the disk. Ideally, each slice of the log file is adjacent. When writing data to the disk, the disk does not need to re-locate the head due to disk fragmentation, which greatly improves the write performance.
After determining the disk type, we need to plan the disk capacity. The disk space of the RAID 5 system that stores database files is determined by the actual number of mailboxes and the size of mailboxes. However, you need to leave a certain amount of free space on this basis. Take an enterprise with 300 users as an example. The mailbox size of each user is 100 MB. Theoretically, the maximum space occupied by the mailbox Store is 300*100 M, that is, 30 GB. Otherwise, we still need to consider the following factors:
1. retention time of the Delete Item. Generally, on the Exchange Server, we will set how long the deleted email will be retained on the Server Store-> Limit-> Deletion Settings ). In this way, you can easily restore the deleted emails. The backup structure of the Exchange Server makes it very difficult to restore a single email. Therefore, setting the Delete Item retention time can help restore information that is accidentally deleted. This time is generally set to 15 to 30 days. We need to note that once this setting is enabled, all deleted emails will not be cleared immediately in the database, so this setting will occupy a certain amount of disk space. If you set the retention time of the Delete Item to 15 days, You need to estimate the number and size of emails deleted by each user within the past two weeks for further planning. If it is set to 15 days, the number of deleted mails is 30% to 50% of the mailbox. This estimation is usually inaccurate. If we want to know the dynamics of each mailbox on the server, we can use a product named "Quest Reports, this webpage-based program will provide the Administrator with a detailed dynamic report on the size of each mailbox. The company's web site is: http://www.quest.com/messagestats/
520) this. width = 520; "onclick = javascript: window. open (this. src); src = "/files/uploadimg/20051206/1011281 .gif" onload =" javascript: if (this. width> 520) this. width = 520; "align = absMiddle border = 0>
Second, the space required for database maintenance. When we sort out Offline fragments of the Exchange Server database Offline defrag, add the stm file to an edb file of a database file of 20 GB ), we need an additional 20 GB space to store the fragmented database files. In addition, when we need to repair the database, we usually make a backup on the server. These spaces also need to be considered.
Therefore, the size of the RAID 5 system that stores database files is generally 1.5 to 2 times the size calculated by the number of mailbox users.
The disk space of log files is determined by the full backup cycle. During full backup, the system automatically clears log files ). If an enterprise performs a full backup once a week, the storage space of the log file disk must be able to hold the log files generated within at least one week. Considering that the backup may fail, the tape drive may fail, and other unexpected factors, this capacity also needs to be reserved ). Generally, we can use an 18 gb scsi disk to form an image array, and dynamically adjust the full backup time based on the log file growth rate.