| William H. Magill on 1 Nov 2005 15:47:35 -0000 |
|
On 01 Nov, 2005, at 08:04, Edmund Goppelt intoned: On Mon, Oct 31, 2005 at 11:52:56PM -0500, William H. Magill wrote:
Nominally, "bear-metal" refers to restoring the OS structure only. Application restore may or may not be included. However, "bare-metal" restores themselves come in different sizes and shapes. A "ghosted" image restores faster than a complete rebuild and configure from "source" media (no, not necessarily recompiling). A restore to an OS release that is 2 or 3 levels behind is different than restoring to latest updates. ... lots of variables. And if you're not dealing with files, what units of storage are you dealing with? Partitions?
Back in the days of VMS (DEC's proprietary system), DEC's backup software allowed one to make a "disk image backup." This "disk image" was used to do bear-metal restores. All that was required was that the disk be prepped with labels, no formatting was necessary as the restore would reconstruct whatever format was on the image. [OS X has a similar capability, called a "disk image" which theoretically could be used in a backup script to accomplish the same thing. I think. However, "ghosting" of PC systems is probably the most common version around today.] DEC's "volume level" restoration always operated at the write speed of
the disk as it took place without the necessity of creating each and
every individual file's catalog entry. The process was much faster
than restoring by individual file. ("Obviously," the number of writes
to create and update the catalog entry is more than the number of
writes needed to restore the file alone.)As I recall you used to work for Penn which has lots of resources--both money and people. I'm in a different situation: it's just me and I have to watch every penny.
I realize you may not be used to working under such constraints, but I'd love to hear your thoughts. How do you think I should go about backing up my 8 or so systems?
One must completely ignore the possible cost until the scope of the problem is outlined and potential solutions defined. Once the scope of the problem, i.e. goals to accomplish, is defined, those goals must be prioritized. If recovery of accidentally deleted files is the highest priority, if Archival Storage of customer data is highest, if protection against catastrophic System failure is the highest, if minimizing down-time is highest -- so be it. Once that list of priorities is defined, one looks at potential solutions, again ignoring the cost. Once various potential solutions are defined, you determine which of those solutions meets the most important of your goals... THEN you cost it out. If costs are a significant constraint, then you know immediately what your "chosen solution" will actually accomplish, and what it will not. Keep in mind that this is an iterative process. Once the proposed solution is costed out and you have to start deleting from your prioritized list, you have to return to the exercise of determining your priorities. Are your original requirements more important than the reduced list? But in the end, you will know just what your solution will accomplish and what it will "cost" in terms of unfilled requirements. There is no such thing as a "one size fits all" backup solution. Every enterprise defines its own "scope." Every solution has pros and cons. You often wind up trading off minimizing downtime for Archival Storage capabilities. Tape is STILL the cheapest Archival media, but it SLOW. "Bricks" (removable disks) can replace tape, but they are expensive. ... etc. [Note, that the cost of tape vs disk for archival storage is really only existent in the small-to-medium "size" market. Once you get to a certain size, the inability of tape to restore in a timely fashion clearly outweighs its cost benefits. In the "large" market, tape is virtually unusable for a multitude of reasons, not the least of which is the simple "capacity of the tape" issue.] If you were a financial oriented enterprise, where the cost of minutes of downtime were measured in thousands of dollars, the fact that is going to take 30 minutes to do a bear-metal restore, can easily be costed out as $30,000! A substantial budget one can use for replicating systems and keeping them around as "hot standbys," even if they are not used for months or years at a time! The primary issue is -- how long is it going to take you to return things to the way they were "before" you lost the system? A 1-TB data store takes A LONG TIME to restore!
"What happens when the architect gets hit by a bus?"
"Somebody else" can be a significant problem. Business continuation ability is a big question. Small businesses are at particular risk because they operate either as a proprietorship or a partnership where one partner does one thing, while the other does something else.
|
|