Matt Ghali, IST–CCS
Over the summer, Central Computing Services (CCS) completed an upgrade to CalMail, UC Berkeley's central email and mailing list support system. The seamless migration of about a terabyte of email storage was completed with minimal downtime and was well received by the UC Berkeley community.
The purpose of the upgrade was to provide better performance for CalMail. CalMail was implemented in January 2004 with a new application and systems architecture. During peak usage periods approaching the end of the spring semester, some users experienced performance problems that we were not previously able to simulate.
CalMail stores mail on a central device called an "NFS filer". This filer serves data to the cluster of five email servers. The huge loads on these email servers, from both inbound email and users checking their inboxes, as well as dramatic increases in spam and virus-laden email, was just too much for the original filers to service. Requests queued up, mail was delayed, and some users experienced unacceptably slow performance in the time it took them to check their mail. We used all expansion space originally planned for the first year in approximately five months.
In May 2004, CCS began circulating a request for quotation (RFQ) to storage vendors, looking for a solution to the capacity problems of the filers. Armed with real-world measurements of demands on the CalMail service during its first semester of usage, the RFQ was focused on obtaining storage that would provide the UC Berkeley community with solid storage volume, speed, expansion, and reliability.
CCS decided to build a storage architecture around products from EMC, including an EMC Symmetrix DMX storage array, and a network-attached file server product called the Celerra. The system stores user email data on more than 100 high-speed disks in the DMX, and presents the data to the CalMail server cluster through a fault-tolerant group of NFS filers in the Celerra. This storage architecture is expandable to meet the growing needs of the campus.
The system has been designed and benchmarked to support 50,000 file requests per second, a five-fold increase over the original devices. The true test of the new system has been the huge increase in traffic during the first few weeks of the fall semester. Metrics monitored by CCS, such as service times, as well as user community feedback, indicate that the new storage is performing well.
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