HPC 2014-15 | Storage


are a storage company.’ Tis is true both for the performance and reliability of supercomputers, and their associated storage solutions as they increase in size on the road to exascale class computing. Rector said: ‘If you have a $100,000,000


supercomputer you want to keep it as busy as possible.’ Tis is part of an overall strategy at DDN that focuses on implementing technology to allow users to use their compute more effectively. Rector said: ‘It is too expensive to move the storage to the compute so we have been working on moving the compute to the data. Users need to be able to move big data sets into the memory.’


Move the compute to the data One way in which DDN has been working on enabling its users to use compute more effectively is through the implementation of the infinite memory engine (IME), a burst buffer for big data HPC applications. Te improvements are implemented through an intelligent soſtware layer that provides a distributed NVRAM storage cache using patented algorithms to eliminate file-locking pressure. Panasas has been developing its own


solutions to increase the performance of their storage solutions. Te release of ActiveStor 16 has seen continued development of the hybrid architecture, introduced in ActiveStor 14, that makes use of flash memory to provide low-latency memory based storage to quickly transfer small files and metadata. Noer said: ‘We are effectively tiering all of


the small files and metadata to flash and that has a tremendous impact on the performance of real world applications.’ ‘When you have all those small files and


the file system metadata clogging up the hard drives you rarely get the sort of performance that you expect from your drive. By putting all that data onto flash you can greatly accelerate the user’s experience.’ Price of storage is another issue, not


because the price of storage is too high but because the storage needs of data intensive markets grow so quickly that storage is becoming a real concern for users that need to archive data for an extended period of time. Panasas’ solution to this problem is to


keep small files and metadata persistently in Flash SSD to achieve exceptional I/O performance that is not possible on hard disk. Larger files are broadly striped


22 The Data Direct Network SFA12K storage platform


across SATA drives for cost effectiveness. Tis hybrid approach delivers optimum performance for a given cost with mixed file workloads, which is the case in almost all HPC and technical computing environments. DDN has implemented object storage


through a pre-configured cloud storage platform, allowing users to archive unstructured data onto the cloud service. Tis not only reduces the cost associated with the performance tier of the storage solution as users won’t need as much capacity, but also


“A significant bottleneck can be the memory or cache used to move large data sets into compute architecture”


allows DDN and its customers to focus on delivering the highest performance possible for the regularly accessed data. Rector said: ‘Object storage allows us to alleviate the pressure on performance storage.’ However, performance is only one


aspect of the requirements of storage in an exascale computing environment. Although performance will always be a key requirement for many applications, fault- tolerance of large scale systems is key to using compute resources efficiently. Claffey said: ‘When you deal with that scale it is imperative that you can provide the kind of reliability and scalability that the industry requires. At Seagate, we can provide that because we have unique intellectual property at every stage of the storage stack.’


Seagate has a distinctive position in


the HPC storage market; not only does it produce the large scale systems but it also produces the drives themselves. Tis provides another layer of expertise in dealing with problems and allows the company to address reliability from the hardware perspective as well as the soſtware controlling the distribution of data across a high- performance storage system. For Panasas, Noer said: ‘It’s much more


than just the possibility of a drive failing. Actually, the more common scenario is that you will get one or more sectors that are unreadable and the rest of the drive is accessible normally. Te unreadable sector error is what is actually most common and the larger the hard drive the higher the probability of this kind of error occurring.’ Noer continued: ‘Tis is a disaster


mitigation scenario, there is a big difference between losing 10 petabytes of storage by having three hard drive failures, to getting a list of 10 files that you have to restore to bring your system completely back up to health and allowing your users to access almost all of the files normally while you are restoring those 10 files.’ Tis level of data protection is a key


aspect of storage technology at exascale. Storage solutions at this scale are used to run critical supercomputing applications oſten taking many hours to complete. Repeating application runs because of hardware failure must be kept to a minimum so that the HPC system can be used efficiently. Noer explained that Panasas


accomplished this using an intelligent per-file distributed RAID architecture that implements triple parity data protection. Noer said: ‘Part of what we accomplished with RAID6+ is actually triple parity protection, where we have, in addition to a RAID6 level of protection against two simultaneous device failures we also have a third level of parity protection that prevents the system from ever having to rebuild in the first place, if you run into sector errors. Te increased demand for storage in both


HPC and enterprise markets is having a positive impact on the technology, as Claffey highlights: ‘Tere is a symbiotic relationship between the needs of the enterprise markets and traditional HPC. Enterprise in particular helps to drive price performance and that feeds back into the traditional markets. ‘Tis provides a feedback loop that


really generates a better technology, a better solution for everyone,’ Claffey concluded. l


DDN


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