How can direct attached storage (DAS) make a comeback if it never left?

July 3, 2012 – 4:25 pm

Have you seen or heard the theme that Direct Attached Storage (DAS), either dedicated or shared, internal or external is making a comeback?

Wait, if something did not go away, how can it make a comeback?

IMHO it is as simple as for the past decade or so, DAS has been overshadowed by shared networked storage including switched SAS, iSCSI, Fibre Channel (FC) and FC over Ethernet (FCoE) based block storage area networks (SAN) and file based (NFS and Windows SMB/CIFS) network attached storage (NAS) using IP and Ethernet networks. This has been particularly true by most of the independent storage vendors who have become focused on networked storage (SAN or NAS) solutions.

However some of the server vendors have also jumped into the deep end of the storage pool with their enthusiasm for networked storage, even though they still sell a lot of DAS including internal dedicated, along with external dedicated and shared storage.

The trend for DAS storage has evolved with the interfaces and storage mediums including from parallel SCSI and IDE to SATA and more recently 3Gbs and 6Gbs SAS (with 12Gbs in first lab trials). Similarly the storage mediums include a mix of fast 10K and 15K hard disk drives (HDD) along with high-capacity HDDs and ultra-high performance solid state devices (SSD) moving from 3.5 to 2.5 inch form factors.

While there has been a lot of industry and vendor marketing efforts around networked storage (e.g. SAN and NAS), DAS based storage was over shadowed so it should not be a surprise that those focused on SAN and NAS are surprised to hear DAS is alive and well. Not only is DAS alive and well, it’s also becoming an important scaling and convergence topic for adding extra storage to appliances as well as servers including those for scale out, big data, cloud and high density not to mention high performance and high productivity computing.

Consequently its becoming ok to talk about DAS again. Granted you might get some peer pressure from your trend setting or trend following friends to get back on the networked storage bandwagon. Keep this in mind, take a look at some of the cool trend setting big data and little data (database) appliances, backup, dedupe and archive appliances, cloud and scale out NAS and object storage systems among others and will likely find DAS on the back-end. On a smaller scale, or in high-density rack deployments in large cloud or similar environments you may also find DAS including switched shared SAS.

Does that mean SANs are dead?
No, not IMHO despite what some vendors marketers and their followers will claim which is ironic given how some of them were leading the DAS is dead campaign in favor of iSCSI or FC or NAS a few years ago. However simply comparing DAS to SAN or NAS in a competing way is like comparing apples to oranges, instead, look at how and where they can complement and enable each other. In other words, different tools for various tasks, various storage and interfaces for different needs.

Thus IMHO DAS never left or went anywhere per say, it just was not fashionable or cool to talk about until now as it is cool and trend to discuss it again.

Ok, nuff said for now.

Cheers Gs

Greg Schulz – Author Cloud and Virtual Data Storage Networking (CRC Press, 2011), The Green and Virtual Data Center (CRC Press, 2009), and Resilient Storage Networks (Elsevier, 2004)

twitter @storageio

http://blogstu.wordpress.com stu
Greg, While there is no shortage of hyperbole in the industry, there definitely are some large trends that are shifting the storage world. Over the last decade, many servers went to diskless configurations in support of shared (networked) storage environments. While you mentioned big data and some other scale-out environments that potentially move back towards DAS, you didn’t mention Flash/SSD solutions which are swinging more hardware and intelligence back towards the server. I agree with your statement that it is rarely an all-or-nothing when it comes to technology shifts; the centralization vs. disaggregation of intelligence tends to be a pendulum swing which is swinging back towards the server and integrated solutions. SAN surely isn’t dead, but the rise of unstructured data, the growth of solutions that can benefit from server-based storage and other solutions have the potential to put a dent in the SAN solution space.
http://twitter.com/cebess Charlie Bess
What will be interesting is the pending revolution that storage class memory will provide, once we move beyond spinning storage and the distraction of flash. Hopefully we’ll check back in a couple of years and these conversations will all appear quaint.
Greg schulz
Hello Stu
and thanks for the notes/comments.
Actually,
I did mention SSD (aka flash) in the above post.
If there
was not enough focus on flash, or particular PCIe flash you can certainly find
a lot more SSD coverage and discussion on that and related technologies other
posts on this site as well as others where I have comments/content.
As for
many servers being diskless, sure, just as with diskless workstations, that has
been the case for a while.
However
there are also a large number of servers shipping with disks (HDD or SSD) as
well as PCIe flash (SSD) cards or PCIe RAID cards being shipped for traditional
purposes, as well as special purpose appliances from database (e.g. little
data) to data ware house, analytics (e.g. big data) to unstructured NAS and
object among others you know the list better than me.
cheers gs
Thanks
again for the comments, hope all is well, say hello to the rest of the wikibon
and siliconangle crew, see you at some upcoming event somewhere.
Greg schulz
Hello Charlie good point about storage class memory, we can as you mentioned check back in a few years and see if that technology takes off as some predict vs. hopefully not following other pending revolutions such as holographic among other storage and memory technologies that ended up on the where are they now list…
Thanks for the perspectives
http://twitter.com/robcommins Rob Commins
Hi Greg -
One thing is for sure – especially in storage: the only thing harder than bringing a new technology to market is making an old one go away. You are absolutely correct about DAS, and the same thing can be said about tape. Ask my pals back at HP what % of their storage revenue comes from tape – most will be floored.
Old habits die hard too. To springboard off Stu’s comment; the hyperbole will continue to buzz for a lonnnnng time.
Greg schulz
Good points Rob, thanks for the comments
Tim Plas
Also interesting to watch what Microsoft is doing w storage in Win Server 2012 / Hyper-V, & other products like SQL Server. Much like they did earlier w MS Exchange. –introducing more replication at the app layer, and keeping multiple copies of stuff, on storage that’s not shared between servers (i.e., on DAS).
Greg schulz
Good points Tim about MSFT (among others) with and without virtualization leveraging DAS (both dedicated and shared).
Pingback: Announcing SAS SANs for Dummies book, LSI edition | StorageIOblog
Pingback: Cloud, virtualization, storage and networking in an election year « Data-Center.BlogNotions - Thoughts from Industry Experts
Pingback: RAID and IOPS and IO observations « Data-Center.BlogNotions - Thoughts from Industry Experts
Pingback: RAID and IOPS and IO observations - StorageIO Blog - IBM Storage Community
Pingback: RAID and IOPS and IO Observations | Daily World NewsDaily World News
Pingback: The Data Center Journal RAID and IOPS and IO observations
Pingback: Putting some VMware ESX storage tips together (Part I) | StorageIOblog
Pingback: The Data Center Journal Putting some VMware ESX storage tips together