Lab test: New EqualLogic firmware takes a load off VMware

Dell’s latest firmware release, version 5, for the EqualLogic PS series of iSCSI SANs brings a number of immediate and significant performance benefits to VMware deployments. Some key new features — including Multipath I/O support and the ability to offload copy operations from hosts to the SAN — are also supported on Windows with EqualLogic’s HIT (Host Integration Tools). Others, such as thin volume cloning and refreshes to the Group Manager and SAN Headquarters administration tools, will benefit all users.

The version 5 firmware also brings dynamic storage tiering to the new Dell EqualLogic PS6010XVS array. (See “InfoWorld review: Dell iSCSI SAN sizzles with SSD, dynamic storage tiering.”)

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Unfortunately, the rollout of version 5 wasn’t problem-free. The initial 5.0.0 firmware, released a few weeks before VMware ESX 4.1, brought with it some unforeseen problems, generally related to upgrading production systems that were running older code. Three months and two iterations later, the new 5.0.2 version appears truly ready for prime time.

That stumble was quite unlike EqualLogic and may have been caused by the rush to release the firmware ahead of the official unveiling of VMware ESX 4.1. Whatever the case, Dell promises that the problems related to the 5.0.0 and 5.0.1 releases have been resolved. This is good news, as the 5.0.2 firmware offers many reasons to upgrade or to add an EqualLogic array to your infrastructure.

Faster VM copies for VMware hosts Traditionally, when VMware needed to copy a virtual machine, it treated the storage as a dumb entity and handled the block-by-block copy normally, by reading and writing the blocks to and from the storage array. With the advent of copy offloading, the ESX host can simply instruct the EqualLogic array to copy the blocks containing the image, and the array handles the copy itself.

In real-world tests, this results in a much faster copy operation and a greatly reduced load on the ESX server. In lab tests, this means that cloning a 30GB virtual machine took just over three minutes with copy offloading and more than nine minutes without. During that test, the CPU of the ESX server was pegged, as several virtual machines running on the host had been pushed to their limits. With copy offloading enabled, there was almost no ESX CPU activity required to complete the operation.

Zero offloading is similar to copy offloading, but while copy offloading is also available to Windows hosts, zero offloading is exclusive to VMware. Rather than require the ESX server to write zeros to storage blocks, such as when deleting a virtual machine, it can instruct the array to write those zeros for it. Again, the result is far lower ESX server CPU utilization and a quicker response.

Another VMware-only feature in version 5 is hardware-assisted locking. Normally, when VMware conducts certain operations — such as powering a virtual machine on or off, executing a VMotion, creating a new virtual machine, or deleting a snapshot — the entire VMFS file system is locked momentarily. When these actions occur sporadically, it’s not much of a problem, but when there’s a run on the VMware farm — such as when a bunch of new VDI desktops are powered on — it can create delays. In this new firmware version, EqualLogic arrays can lock only the blocks required to perform that operation, allowing the VMFS file system to continue to serve other requests. Thus, there are no delays felt by concurrent operations, which can help significantly when the file system is getting hammered.

Thin clones: Multiple volumes in one Another new feature is thin clones, which provide the ability to clone a volume without consuming additional storage space. Thin clones can be made of any existing volume, though any volume used as a source for thin clones can no longer be accessed directly. The cloning process is very quick, as it’s essentially creating a volume of pointers to the source, but otherwise thin clones function as any other storage volume. New data written to the clone inhabits its own space on the storage array, but reads from the cloned data come from the source volume.

Thin clones are ideally suited to use cases where a number of servers or desktops might share a common OS installation on a source volume, as the storage requirements for those systems become significantly smaller than dedicating a full volume to each. Thin clones also ease replication, as only the data written after the thin clone was created needs to be pushed to the replication partner.

Another use case might be large data sets found in development or read-only databases, where the source volume contains a fixed data set. A thin clone can be created for anyone who needs to work with that data without disturbing other processes that need to access or manipulate the same data.

Finally, a thin clone can subsequently be converted into a full volume, but that volume necessarily requires the full amount of space allocated to both the source volume and the data written to the clone itself.

EqualLogic Group Manager refresh There are some cosmetic and usability changes in the new firmware as well, with the addition of quick-access view selection buttons in the bottom left of the EqualLogic Group Manager administration application. There’s also context-sensitive help buttons, enhanced view modifiers, monitoring and event log updates, and a new alarms and operations bar at the bottom. While the overall look and feel of the GUI hasn’t changed substantially, these new features are welcome and quite useful. Those with previous experience with the UI will find themselves right at home.

At the back end, there are other additions. EqualLogic has had support for Perl-based scripting through a telnet interface for a while now, and it has added support for Python scripting through an SSH-based interface. The two are exclusive, meaning you can’t use Perl via SSH or Python via telnet, but providing the Python support does allow for broader, more secure scripting support.

A new user role, dubbed Volume Admin, has been added to this version of the firmware as well. Users assigned to this role can be given restrictions on which storage volumes they can access and modify, as well as an overall disk usage quota that crosses all accessible volumes. This means it’s now possible to support multitenancy with an EqualLogic array, while ensuring that users cannot consume more resources than they are permitted.

Multipath I/O for VMware Although it’s not part of the new firmware, Dell has released an MPIO (Multipath I/O) plug-in for VMware ESX that enables multipathing support from an ESX 4.1 host to an EqualLogic array. When installed, this plug-in obviates the need to bond interfaces or do any switch-assisted pathing for storage links, and it automatically balances traffic through available interfaces to the arrays. As with any third-party MPIO plug-in for VMware, this feature requires the VMware Enterprise or Enterprise Plus editions.

The MPIO plug-in creates two paths to each storage group member, then chooses the path with the least queue depth to communicate, reducing latency and increasing overall throughput. This also protects against link failure; if a link goes down, all storage communication is shunted to the remaining links.

An MPIO plug-in is also available for Windows Server 2003 and Windows Server 2008 hosts.

New EqualLogic SAN HQ As if that weren’t enough, there have been significant updates to EqualLogic’s SAN HQ monitoring and trending package. These include support for firmware version 5, including thin clones; support for the PS6000XVS and PS6010XVS arrays, configurable custom home page views, replication and capacity views across groups, reporting enhancements; support for favorites, or bookmarks of commonly accessed reports and information; and reporting breakouts for several lower-level functions such as replication and SSD write cache statistics.

SAN HQ has been a very useful tool in day-to-day administration of EqualLogic SANs, and the new version builds on that foundation, allowing even more granular inspection of how individual arrays or groups of arrays are behaving and helping to pinpoint potential trouble spots, or provide trend analysis of storage use over time.

All in all, the new features and capabilities present in the new EqualLogic firmware are very impressive and highly desirable for anyone using EqualLogic arrays in any context — especially virtualized infrastructures. Now that EqualLogic has cemented version 5 and the 5.0.0 and 5.0.1 hiccups are history, there’s every reason in the world to upgrade existing arrays and plenty of reasons to look at EqualLogic storage as an extremely capable iSCSI solution.

This story, “Lab test: New EqualLogic firmware takes a load off VMware,” was originally published at InfoWorld.com. Follow the latest developments in storage, hardware, and virtualization at InfoWorld.com.