March 16, 2016

Issues with MS SQL Server Standard edition in AWS

Issues with MS SQL Server Standard edition in AWS

1. Database Mirroring and index maintenance
MS SQL Server Standard edition in AWS allows  synchronous mirroring only.In synchronous mirroring, the additional log being generated could overload the network link between the principal and mirror. This will slow down the hardening of regular transactions in the mirror’s transaction log, and thus led to a decrease in transaction throughput on the principal.

Solution: log stream compression

SQL Server 2008 introduces a new feature called "Database Mirroring Log Compression". With SQL Server 2008, the outgoing log stream from the principal to the mirror is compressed, thereby minimizing the network bandwidth used by database mirroring. In a network constrained for bandwidth, compressing the log stream helps improve the application performance and throughput.Log compression compression rates of at least 12.5% are achieved.


2. You can’t cluster in EC2… with SQL Server 2008 R2
You can’t cluster in EC2. There’s no shared storage. EBS volumes can only be attached to a single server at a time. You could share the drives, but you really shouldn’t do that. You could use some Windows based SAN system that mounts drives and pretends it’s a SAN, but without any guarantees of performance or longevity, why would you want to?


HA options : Log shipping, mirroring and transactional replication

3. Scaling SQL Server in  EC2: SCALING UP

There’s a finite limit to how much you can scale up SQL Server in EC2. That limit is currently 8 cores and 68.4GB of RAM. Those 8 cores currently are Intel Xeon X5550s that clock in at 2.66 GHz, but that will have changed by the time you’re reading this.

4.Backup or restore database:


Backup or restore database activity on AWS SQL Server standard edition with EBS disks have following issues.
1. Connections timeout
2. I/O requests taking longer than than usual
3. The timeouts was not just from the database being restored, but from all databases as  EBS drives get clogged up causing IO to bunch up severely.


Some recommendations:
1. It looks as though the disk reads are maxing out the EBS connection, doublecheck EC2 tuning settings?
2. Choose an EBS–optimized instance that provides more dedicated EBS throughput than your application needs; otherwise, the connection between Amazon EBS and Amazon EC2 can become a performance bottleneck.
You can enable EBS optimization for the other instance types that support EBS optimization when you launch the instances, or enable EBS optimization after the instances are running. 

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