Monthly Archives: May 2012
It is somewhat surprising just how many skilled IT specialists still shy away from eliminating traditional internal boot disks with a Boot-from-SAN process. I realize old habits die hard and there’s something reassuring about having the O/S find the default boot-block without needing human intervention. However the price organizations pay for this convenience is not justifiable. It simply adds waste, complexity, and unnecessary expense to their computing environment.
Traditionally servers have relied on internal disk for initiating their boot-up processes. At start-up, the system BIOS executes a self-test, starts primitive services like the video output and basic I/O operations, then goes to a pre-defined disk block where the MBR (Master Boot Record) is located. For most systems, the Stage 1 Boot Loader resides on the first block of the default disk drive. The BIOS loads this data into system memory, which then continues to load Stage 2 Boot instructions and ultimately start the Operating System.
Due to the importance of the boot process and the common practice of loading the operating system on the same disk, two disks drives with a RAID1 (disk mirroring) configuration is commonly used to ensure high availability.
Ok, so far so good. Then what’s the problem?
The problem is the disks themselves. Unlike virtually every subsystem in the server, these are electro/mechanical devices with the following undesirable issues:
- Power & Cooling – Unlike other solid-state components, these devices take a disproportionately large amount of power to start and operate. A mirrored pair of 300GB, 15K RPM disks will consume around .25 amps of power and need 95.6 BTUs for cooling. Each system with internal disk has its own miniature “space heater” that aggravates efforts to keep sensitive solid state components cool.
- Physical Space – Each 3.5 inch drive is 1” x 4.0” x 5.76” (or 23.04 cubic inches) in size, so a mirrored pair of disks in a server represents an obstacle of 46.08 cubic inches that requires physical space, provisions for mounting, power connections, air flow routing, and vibration dampening to reduce fatigue on itself and other internal components.
- Under-utilized Capacity – As disk drive technology continues to advance, it becomes more economical to manufacture higher capacity disk drives than maintain an inventory of lower capacity disks. Therefore servers today are commonly shipped with 300GB or 450GB boot drives. The problem is that Windows Server 2008 (or similar) only needs < 100GB of space, so 66% of the disk’s capacity is wasted.
- Backup & Recovery – Initially everyone plans to keep only the O/S, patches and updates, log files, and related utilities on the boot disk. However, the local disk is far too convenient and eventually has other files “temporarily” put on it as well. Unfortunately some companies don’t include boot disks in their backup schedule, and risk losing valuable content if both disks are corrupted. (Note: RAID1 protects data from individual disk failures but not corruption.)
Boot-from-SAN does not involve a PXE or tftp boot over the network. It is an HBA BIOS setting that allows SAN disk to be recognized very early in the boot process as a valid boot device, then points the server to that location for the Stage 1 Boot Loader code. It eliminates any need for internal disk devices and moves the process to shared storage on the SAN. It also facilitates the rapid replacement of failed servers (all data and applications remain on the SAN), and is particularly useful for blade systems (where server “real-estate” is at a premium and optimal airflow is crucial).
The most common argument used against Boot-from-SAN is “what if the SAN is not available”. On the surface it sounds like a valid point, but what is the chance of that occurring with well-designed SAN storage? Why would that be any different than if the internal boot disk array failed to start? Even if the system started internally and the O/S loaded, how much work could a server do if it could not connect to the SAN? The consequences of any system failing to come up to an operational state are the same, regardless if it uses a Boot-from-SAN process or boots up from internal disks.
For a handful servers, this may not be a very big deal. However, when you consider the impact on a datacenter running thousands of servers the problem becomes obvious. For every thousand servers, Boot-from-SAN eliminates the expense of two thousand internal disks, 240 amps of current, the need for 655,300 BTUs of cooling, greatly simplifies equipment rack airflow, eliminates 200TB of inaccessible space, and measurably improves storage manageability and data backup protection.
Boot-from-SAN capability is built into most modern HBA BIOS’s and is supported by almost every operating system and storage array on the market. Implementing this valuable tool should measurably improve the efficiency of your data center operation.
We’re struggling back from the depths of recession, but IT budgets remain tight. The business community is demanding an ever-increasing amount of functionality from the datacenter. Managing IT today is an exercise in being-between-a-rock-and-a-hard-place.
However in the midst of this seemingly impossible situation, there are bright spots. Most datacenters are a veritable treasure-trove of opportunity for efficiency improvements. Some examples include:
- Typically over 90% of all data sitting on active disk has not been accessed in over 6-months.
- An average physical server (non-virtualized) is less than 30% utilized.
- Floor-space for a 42U equipment rack costs around $3000 per month (or $36,000 per year, per rack). That equate to over $850 per U (1.75 inches), per year!
- Replacing rack servers with blade servers can reduce the amount of rack space by at least 36% (typically much more).
- According to Intel, upgrading servers to newer, more powerful systems can yield a consolidation ratio of between 4:1 and 7:1.
- Standardizing on 45U high equipment racks, rather than 42U racks will reduce your datacenter foot print by (1) rack for every (14) equipment racks installed.
- The purchase price for multi-tiered storage equipment is normally 25% – 35% less than traditional storage arrays.
- Replacing boot disks with boot-from-SAN technology may eliminate literally hundreds of underutilized disks, along with the power and cooling they require.
- 2.5 inch disk drives need 40% less energy (and cooling) than a 3.5 inch disk drive equivalent of the same capacity.
- In a properly managed environment, LTO tape media will store seldom-used data for up to 30-years with a 99.999% recovery rate – at under $.03 per GB!
- A well-designed SAN topology can lower the fibre channel port cost from $1800-per-port to around $300-per-port (an 80%+ reduction in cost)!
- Well-designed and properly delivered IT training can increase productivity by 17% – 21% per FTE.
So where to start? The quickest way is to perform a high-level assessment of the datacenter to identify the most promising opportunities. This can be done by internal personnel, but it is a task most effectively done by an outside IT consulting firm that specializes in datacenter optimization. They can devote the time necessary to promptly complete the task, and are not biased by day-to-day familiarity with the equipment that may mask issues. Additionally, an professional datacenter consultant can deliver an industry-wide perspective, suggest best practices, and offer out-of-the-box thinking that is not influenced by an organization’s current culture.
Once all areas for improvement have been exposed and documented, the data should be transitioned into the architectural development and planning cycle to ensure any changes will not adversely impact other areas of operation, and are executed on a manageable and sustainable timeline.
Unfortunately there is no “magic cure” for a difficult economy or anemic IT budgets. However, most datacenters offer more than enough opportunity to enable you to shave 20% to 30% off the operating budget.