Clouds mass over data warehousing
Comment Suddenly the data warehousing sector seems to be hotting up. There's EMC's new competency centre and now Kognitio's in-memory data warehouse which threatens to brush server vendors aside if the idea gets adopted big time. How does that one work?
The story goes like this: Cluster lots of servers together in a shared-nothing architecture and use parallelising data-warehouse SW - WX2 in this case - to treat them as a single but very parallel resource. The servers all execute different threads of queries against the data that is stored in the servers' DRAM as an in-memory database. All other data, such as query results or a fraction of the data warehouse that is not in memory, is stored on disk - the servers' directly-attached disk and not in a networked disk resource such as a SAN or a NAS box.
Generally, with a disk-based data warehouse, only a fraction of the data is stored in memory, and query results executed against this are only looking at a data sample and not the full warehouse. Results from a full-warehouse query are statistically much more likely to be correct.
Roger Gaskell, the chief technology officer of Kognitio, says the firm is currently bidding for a 40TB data warehouse and its bid is less expensive than the installed DW system based on storage arrays and many servers. But how can 40TB memory-based system be cheaper?
It's cheaper in memory than on disk
The prospective customer, a large US business with a retail interest, currently has a 600TB data warehouse stored on a Fibre Channel-accessed modular drive-array resource, with queries processed by high-cost servers. Kognitio's bid is for 600 servers in a cluster - or, more accurately, a grid set-up - which collectively have 40TB of DRAM and 600TB of disk, but server direct-attached disk, and not modular arrays.
The servers are low-cost Dell or HP X86 servers and the cost of this set-up will be around $4,000,000, whereas the cost of the installed system was $5,000,000. Gaskell said that because the servers are so cheap, "The disk storage is almost free."
Gaskell told The Reg that the Kognitio system will be radically faster in answering queries - up to 80 times faster - than the disk-based system. The reason that the customer is looking to replace or augment the existing DW array-based system is because complex queries can now take up to four or more hours, and they'll be answered in three to six minutes on the in-memory Kognitio warehouse.
If this is true - that is, if the proposed system really is 80 times faster and a fifth less expensive - then it's a steal. Gaskell wouldn't identify the prospective customer because that company didn't want to upset its incumbent vendors. You can see why: Kognitio's technology renders DW use of storage arrays redundant. This customer still gets 600TB of disk but he'll be paying a much lower server-drive price rather than storage-array prices. Gaskell says, "You can get a terabyte of disk for about $400 on an HP rack-mount server."
Why not use flash storage instead of DRAM? Wouldn't it be cheaper still? Yes, it would, said Gaskell, but as a drive-array substitute it would only be two to three times faster than disk instead of 80 times faster, and the whole reason for going in-memory is to achieve the speed needed to get real-time response to queries.
Why not use a single big chunk of DRAM, like a TMS RamSan? "We have a shared-nothing architecture for reliability," said Gaskell. "If a server goes down we can work around that," meaning that if links to the RamSan or the RamSan itself goes down then, oops, your real-time response just went dead.
DAAS - Data warehousing as a service
For customers who can't afford their very own $4,000,000 in-memory data warehouse, Kognitio offers DAAS (data warehousing as a service). A customer's data is stored in a Kognitio data centre, with a disk pack-based initial data upload and subsequent nightly or weekly updates. Users are charged on a TB used/hour basis.
Kognitio CEO Roger Llewellyn does not want to hear this service described as a data warehouse in the cloud. He says that cloud computing means you don't know where your data is, and that the records in data warehouses are so sensitive, so confidential, that customers must know exactly where they are, and be confident that their data is held securely with access restricted only to the select few. They don't like the idea of a cloud data warehouse at all.
I guess we can use the term "private cloud", though - and "cloud" is a term that's becoming so pervasive that Llewellyn may be fighting an unwinnable battle.
A company called Loyalty Management Group operates a private DW cloud that stores all Sainsbury's EPOS (electronic point of sale) data and sells access to it to Sainsbury's suppliers. If Heinz, for example, wants to know if a baked-bean promotion was successful it can use the LMG facility to check sales through Sainsbury's to find out. There is two years' worth of EPOS data in the warehouse, billions of records, and even shopping-basket analysis queries, said to be the most complex, have results delivered in minutes.
Privately-owned Kognitio is UK-based with just over 80 employees. It has a seven-person US presence and thinks half of its US business in the next year or so will be DAAS-based. The combination of in-memory DW/BI systems providing less expensive and very much faster analysis than disk-based DW/BI, together with private-cloud DAAS, could be a shake-up call to an industry happily in bed with drive arrays. ®