All-Flash Arrays: Benefits and disadvantages

All-Flash Arrays: Benefits and disadvantages

With more and more storage and speed needed in the age of big data, All-Flash Arrays sound like the perfect solution to handle huge amounts of data. And since the prices for both Flash NAND chips as well as SSDs (solid state disks) have fallen over the years, these questions arise: What is an All-Flash Array? And why should I go for an All-Flash Array?

Simply put, an All-Flash Array is a solid state storage (SSD) disk system that contains multiple Flash drives instead of traditional spinning hard disks.

Well, the second question is not easy to answer! The best reply here is: It depends! That is because like everything in technology it has it benefits and its disadvantages. All Flash Arrays are targeted mostly for extremely high-transaktion or throughput application where speed and time are crucial. Financial trades for example would be such a use-case as well as huge e-commerce sites or on-demand streaming services. Here the input and output (I/O) ratio the application requires is the main thing to consider and since the I/O rates of normal as well as enterprise hard disk drives remain unchanged and low for a couple of years now, All-Flash Arrays are the answer here.

Regarding I/O speeds per second, DellEMC quotes IDC for example to state that a system that needs 200000 IOPS (inputs/outputs per second) to run an application on, only needs a 10 high-end SSDs compared to 1000 HDDs. Because of that less server in total are needed to have the same performance as before. Additionally less energy is consumed by an All-Flash solution as well as less storage administration time is needed to manage such a system. Time that for example in case of a server farm can add up to a lot of money being saved or spend otherwise during the year.

And with new designed storage controllers build inside modern systems, All Flash Arrays have all the necessary features that HDD based system nowadays have, too: Deduplication, Compression and Thin Provisioning as well as Snpashots, Clones, RAID, Encryption or API support. With build-in RAID support the user is therefore able to construct a normal RAID 5 out of several SSDs with the data security such a system provides.

So when I/O speed and time are the main benefits of All Flash Arrays, what are the disadvantages, then?

That´s quite simple: It is the price, stupid! Even though Flash and SSDs have become cheaper the are still more expensive compared to HDDs. So buying a new All-Flash Array can be a costly experience compared to a normal HDD system, which can only pay off when you use it for quite a long time.

The other disadvantage is that SSD based systems such as these All-Flash Arrays have a technology downside: Technology-wise are Flash chip best when data is only written on them once and then read many times. Flash chips only have a specified life span based on data writes. So the trick to make as few writing processes as possible to extend the life span of a All-Flash Array. The other technology problem is the SSD trim command.

The SSD trim command is a technique to avoid write inputs/outputs (I/O) that makes the life span of a Flash chip shorter every time. Trim allows the operating system to flag blocks of data to be erased, when they have been released from the local file system. That means that the process of automatic erasing starts way in advance before new data is being written on the „empty“ storage space.

Because of these facts and to avoid loss of data that is needed in the future – business related or material that has to be archived because of compliance or legal reasons – Flash based systems should only be used in environments were data is „only“ read or analyzed. So using an All-Flash array can be used and shows its enormous benefits in speed is for example a great idea for streaming servers like youtube and others.

Also using these machines for big data analysis or running huge data bases on them is a possible use case. For all data that needs to be either stored permanently or is being changed frequently you should either choose a disk based storage or server solution or a hybrid storage solution which consists out of both media types – SSDs as well as traditional hard disk drives (HDDs). This way data that is analyzed or frequently addressed but not changed can run through the SSDs, while the other data is stored within the disks. Or the data that is most-likely- to-be-accessed is stored on the faster Flash chips while the other data is based on a traditional HDD. This way chances that crucial data is lost is minimized.

However, in an event that data is lost in an All Flash Array, there is still the chance that a professional data recovery service provider like Ontrack Data Recovery will be able to recover files. In many cases the data structure is the same as with a normal low-end RAID system and can therefore be reconstructed. Additionally the experts have special tools to rebuild a RAID based or special high-end data structure, so that the data can be found and made accessable again. Therefore in case of a data loss with an All Flash Array the user should immediately stop running the system, try to shut down the usual way with no sudden power outage and then contact the specialists as fast as you can.

But as pointed out before this is only possible when the build-in trim command in the system is either inactive or the space where lost data on the storage was originally located on was not used for saving new data. Then even the most experienced data recovery expert cannot do anything for you anymore.

Find more information on All-Flash Arrays here:

http://searchstorage.techtarget.com/essentialguide/Flash-storage-Guide-to-enterprise-all-flash-storage-arrays

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