Advantages of DAS over SAN storage in Exchange 2007

scr data

scr data — Sat, 26 Apr 2008 10:24:31 GMT

PingBack from http://demarion.cheapnewssite.com/scrdata.html

re: Advantages of DAS over SAN storage in Exchange 2007

Brian — Thu, 07 Aug 2008 22:49:48 GMT

Hi Johnann,

the point about "Cost reductions in excess of $10 million per year" were driven mostly through reduction of TAPE, while your total terabytes and number of servers increased as compared to the consolidated architecture common with Exchange 2003.

Is this a marketing blog, or a technical blog?

re: Advantages of DAS over SAN storage in Exchange 2007

jkruse — Fri, 08 Aug 2008 01:05:36 GMT

Hi Brian,

My blog is for a technical audience, but you’ll find that a lot of what I talk about has a business focus.

Technical knowledge is all well and good but you need a business reason to drive technical projects, and that’s a large part of what my role at Microsoft is – assisting to Enterprise customers to translate technical capabilities into business value, a good example being a reduction in storage costs with Exchange 2007.

You’re correct that in the linked article over $5-million out of the $10-million in cost savings is due to elimination of tape backups, but that means there is still $4-5-million in further cost-savings that are not due to tapes.

There are some additional points I think you’ve overlooked:

• CCR and DPM are the technical enablers of this tape elimination, while SAS disks (DAS) are the cost (business) enabler. Without moving to DAS it would not have been feasible to implement CCR/DPM, and thereby eliminate tapes.

• You mention that our “total terabytes” increased. Exactly – that is the whole point! By using DAS rather than SANs we were able to *increase* our mailbox quotas by *10-times* at a *lower cost* than before.

• You mention that our “number of servers” increased. Sorry but I must have missed that but – my reading of the article suggests that we reduced from 62 Mailbox servers (124 physical cluster nodes) to 34 Mailbox servers (68 physical cluster nodes)?

• That said – CCR means that we have 2 Mailbox servers (Active/passive) for every cluster, each of which has a copy of the data. But again the point is that we increased our quotas by 10-times, and when you factor in CCR that really means we are storing 20-times as much data, but again this is at a lower cost than before.

• The only way we were able to achieve this was by moving to DAS – storing 20-times the data on SANs may be technically possible, but would have been completely cost prohibitive.

Cheers,

Johann

re: Advantages of DAS over SAN storage in Exchange 2007

bob — Wed, 10 Sep 2008 21:54:37 GMT

Interesting post. I understand your point about MSIT but it was not SAN technology or protocols per se, but the choice of SAN (vendor) that drove the expenses so high and thus the 200MB quota.

There are many extremely fast, extremely robust, yet cost-efficient SAN implementations that deliver everything you tout for DAS and then some. I have used DAS, SAN and even NAS for Exchange, and there is no question that SAN is the way to go at any reasonable # of mailboxes for a business. After all, the purpose of SAN is to provide shared storage, not siloed.

re: Advantages of DAS over SAN storage in Exchange 2007

jkruse — Thu, 11 Sep 2008 01:06:57 GMT

Hi Bob,

That is a good point - the cost of storage is of course going to vary from vendor to vendor, and this is specific to the prices that we were able to get in MSIT.

Personally I have yet to see a SAN environment that is anywhere near as cheap or cost efficient as DAS for Exchange, but YMMV.

SANs are all about shared storage environments, but best practice for Exchange is to put it on dedicated storage (spindles etc) within the SAN, which is really creating a silo within the SAN. Here's an out-take from the linked case study:

" Concerns that DAS would create storage silos and hidden operational costs Another obstacle that prevented Microsoft IT from initially seeing CCR on DAS as a viable solution for Mailbox servers was the fact that DAS attaches directly to each cluster node, which creates individual storage silos. From a SAN point of view, it is an overwhelming proposition to create a large number of individual storage locations in the corporate messaging environment. In a SAN environment, ongoing costs for storage allocation, capacity management, performance management, and troubleshooting can quickly exceed the initial investment in hardware and installation. By assuming that this issue of hidden ongoing costs would also apply to DAS, Microsoft IT saw any initial DAS savings potential dwindle rapidly. Today, with the benefit of operating for more than 18 months of CCR on DAS in production, it is easy to say that DAS storage is "designed once and never touched again." However, in early 2006, Microsoft IT was unable to verify that there is truly no need for DAS capacity and performance management beyond the initial storage design. Replacing broken disks, cables, or redundant array of independent disks (RAID) controllers is merely a part of standard hardware maintenance. Downtime due to storage or other node failures is less than two minutes of failover time in a properly designed, CCR-based Mailbox server, and data loss is greatly reduced due to redundant copies of messaging databases on individual cluster nodes. In fact, when CCR on DAS is compared with shared-storage clusters on SAN, it is noticeable that there is less chance for data loss and less need for database restores from backup because CCR eliminates the data instance used by the active node as a critical single point of failure. CCR on DAS also does not create new storage silos. It merely moves the existing storage silos—which dedicated, exclusive Exchange Server storage represents in a shared SAN environment—out of the high-maintenance, high-cost environment into a low-maintenance, low-cost alternative. "

And of course another major driver for us moving to DAS was an extended outage caused by SAN failure:

" a SAN storage array failure occurred, taking down multiple Mailbox servers, and causing an outage and the loss of 8,000 production mailboxes. It took three days to bring the systems back online, and the worst news was yet to come. Through a combination of unfortunate circumstances, the most recent tape-based backups were also irretrievably lost. Microsoft IT was unable to restore the most recent data, and 8,000 users, including employees, partners, contractors, and vendors lost e-mail data. It was a horrible week for Microsoft IT and the Exchange Server product group alike. It showed not only the critical nature of shared storage as a single point of failure in the Mailbox server architecture, but also the vulnerability of an IT organization if it has to depend on tape-based backups as the primary means to recover from storage failures. "

CCR gives us hardware redundancy (e.g. we are still using RAID), data redundancy (two verified copies of the database, automatic failover), and with SCR a 3rd copy of the data with full site/datacentre redundancy... all out-of-the-box at no extra cost aside from the extra servers/disks.

re: Advantages of DAS over SAN storage in Exchange 2007

anupama — Tue, 02 Dec 2008 08:22:54 GMT

what u given differs from heading

its quite opposite

Do You Really Need A SAN Anymore?

Johann's Unified Communications — Sun, 14 Dec 2008 12:46:25 GMT

I have many interesting conversations about my post on Advantages of DAS over SAN storage in Exchange