According to Joe Volesky, senior systems administrator for the academic computing and networking services department at Colorado State University (CSU), his shop was selected by Microsoft as a beta tester for Exchange 2007 last June. Historically, the company had used Fibre Channel storage area networks (SAN), most recently an EMC Clariion CX400, but he was told by Microsoft that the new 64-bit operating system and performance enhancements in the new Exchange that keep mailboxes in memory made iSCSI a more viable storage medium for large email stores.
"We based a lot of our storage decisions over the last year on our switch from Exchange 2003 to 2007," Volesky said. CSU, which has 3,400 Exchange mailboxes, was attracted to the potential cost savings of implementing an iSCSI SAN instead of Fibre Channel. "Once we felt the performance would no longer be an issue, we knew iSCSI would also be a little more straightforward since our staff is very familiar with IP and Ethernet."
Volesky said he looked at two other IP SAN products -- one from LeftHand Networks Inc. and one from EqualLogic. With LeftHand, Volesky said, the price was affordable, but he felt more comfortable with the design of EqualLogic's arrays."We already have an Exchange cluster with three active servers and one passive server," Volesky said. LeftHand, meanwhile, sells software through meet-in-the-channel deals with server vendors. Each LeftHand SAN is actually a cluster of servers itself. "We would have had more systems in the mix with LeftHand, and we just felt the EqualLogic approach would be more like what we were used to in storage."
EqualLogic was also more affordable than EMC's CX3-40. Volesky said the university paid $130,000 for 8 TB of usable storage with software, including replication and snapshot, included at no charge.
According to EMC spokesperson Hadley Weinzierl in an email to SearchStorage.com, "We don't have details on the negotiations that took place with this particular customer, but EMC's systems are priced competitively with other vendors, and our software pricing allows customers to pay for what they will actually use … we [also] offer more choices on the replication front, including support for snapshots and clones, along with asynchronous and synchronous remote replication."
There is one feature Volesky said he misses about EMC's products, namely the active-active controller configuration on Clariion arrays that makes firmware upgrades less disruptive. With the EqualLogic SAN, according to Volesky, the array is technically capable of live firmware upgrades, but Volesky said the university lost connectivity to the Exchange cluster in the past when attempting live updates. "There are special instructions in EqualLogic's firmware release notes regarding settings around the iSCSI initiator during firmware upgrades. We set those but still felt uncomfortable, given that we've seen the array doesn't maintain connection to the devices when it reboots," he said. "For data protection purposes, we just disconnect the arrays when updating."
"[He] is aware of the choices and opted for one of the more conservative approaches involving taking his mail stores down, so there was zero risk of any problems," according to Eric Schott, senior director of product management at EqualLogic, in an email to SearchStorage. "[The] suggestion that EqualLogic enable upgrades of our controllers one at a time is a good idea that we're currently implementing for release later this year."
Exchange 2007 and storage
Using a SAN back end is a far less expensive proposition than filling four servers with 8 TB of local disk, and having centralized storage makes management easier as well, but the tradeoff, Volesky said, was the expense, even at the lower price offered by EqualLogic.
"We have four Dell Inc. PowerEdge 2850s with 12 GB of memory each, but even all together they're still a lot cheaper than the storage," Volesky said, estimating the price of each server at $6,000.
But, Volesky said, so far Microsoft's claims about performance have been proven true. The key is the ability to keep frequently accessed data in server memory, which means fewer disk IOPs on the back-end system, whether Fibre Channel or iSCSI. For the last two months CSU has been conducting performance profile testing on users who are still on the separate 2003 single server and users on the SAN with Exchange 2007. The maximum IOPs per user -- number of times the system must access disk in order to perform an operation, rather than accessing memory -- on 2003 is 1.1 and on 2007, it's less than 0.5, meaning Exchange 2007 is less than half as likely to require disk I/O to perform the same functions. That, combined with the clustered servers and the automatic load balancing performed by his three PS300E arrays, make the performance picture night and day between the two Exchange systems, according to Volesky.
The clustered server/shared storage approach has also helped the university with email backup, Volesky said. Currently, backup copies of data are passed first to a separate partition on the EqualLogic array as nearline disk storage, then sent to the passive server in the Exchange cluster for backup to tape using IBM's Tivoli Storage Manager (TSM). Consolidating backup and server failover onto the passive cluster node has saved on the cost of a separate backup server for now, Volesky said, though the university also plans to replicate to another EqualLogic SAN, once more IT funding becomes available to purchase it next year.