The inspiration for VirtuStor was to build enterprise grade storage using commodity off the shelf components, ensuring enterprise grade reliability, performance, and scale that IT organization demand of traditional SAN storage.
The case for using servers to build SAN storage appliances
Though current generation of SAN based storage appliances do support most of the features required by enterprises, these appliances are still expensive. For instance if you compare the cost of a mid-tier hybrid storage appliance to physical servers for the same specs (CPU, RAM, SSDs, HDDs, and NICs), the storage appliances from big brand OEMs cost about $2/GB, in comparison a server with similar specs costs just 10cents/GB.
Also the customer is locked in with the storage OEM for replacement parts, service, and support.
Back a decade ago, purpose built processors and storage media were required to build storage appliances, which resulted in a higher price tag for enterprise storage. This is not the case anymore since all the components required to build a storage appliance are now available off-the-shelf.
Cloud service providers (SPs) like Amazon, Microsoft, Google, have pioneered the use of commodity servers to build their own cloud storage platform.
In large part because of such high volume utilization of server hardware by cloud SPs that cost of hardware components has reduced drastically.
Cloud SPs build their storage software in Linux, which they then contribute back to the open source community. Since such software is open source, it can also be freely used by enterprises to build their own on-premises storage in the same fashion as these web scale operators.
Another advantage of using servers, is that enterprise storage of any capacity and performance can be built by simply mixing and matching components – motherboards, chassis, memory, SSDs, HDDs, and NICs, that all server vendors let you to do now. So enterprise IT organizations have a lot more choice in tailoring the storage appliances to their requirements using commodity servers than with big brand OEM storage.
So the idea is to ride the coattails of the cloud movement to build fast, fault tolerant, yet cheap on-premises storage using physical servers much like how Google, Microsoft, and Amazon do it
VirtuStor – Server SAN software to convert a cluster of servers to SAN storage
VirtuStor is Linux based software installed on bare metal physical servers that clusters any physical servers and makes this cluster of servers appear as a traditional iSCSI SAN storage.
A minimum of three servers are needed in a VirtuStor cluster, and this cluster of servers appears as a single traditional iSCSI storage appliance/target.
Considering that a 3.5 inch hard drive now carries 10TB capacity and costs only $300, and a server with 200TB of storage costs under $20,000, large amounts of SAN storage can be put together for cheap using VirtuStor running on commodity servers.
You can hot add servers to this cluster, with capacity and performance scaling linearly as you add servers. You can mix and match servers, HDDs, and SSDs of any make, model, and antiquity in this cluster. Unlike branded OEM storage, there is no vendor lock-in for hardware.
VirtuStor server SAN cluster can be managed with a single GUI no matter how large the cluster.
VirtuStor protects against hardware failure by replicating data to one more server in the cluster, hence the requirement for a minimum of 3 physical servers in the cluster, so that storage is unaffected even with one server failure.
VirtuStor can be configured in all-SSD, hybrid SSD+HDD, or all-HDD configurations.
For customers running VMware, a high performing, competitively priced storage configuration is to use hard drive based VirtuStor server SAN for backend storage complimented with VirtuCache + in-host SSDs in the VMware hosts. VirtuCache will cache ‘hot’ data from hard drives in the VirtuStor server SAN to in-host SSDs and thus provide all-flash array like performance from the all-HDD VirtuStor. We highly recommend deploying SSDs in the VMware host rather than in VirtuStor servers because SSDs perform at higher speeds/lower latencies when in the host than if the same SSDs were installed in VirtuStor servers. This because with VirtuCache, SSDs are closer to the VMware host CPU that consumes ‘hot’ data instead of being behind the network and storage CPUs as is the case when the SSDs are in the VirtuStor server SAN.