Main > Everything Else

Raid 5 guestions??

<< < (6/12) > >>

shmokes:
I've seen a RAID 5 array refuse to rebuild itself after a drive failure and I've known at least two or three other people (professionals) who have personally had the same experience.  I've seen them rebuild just fine a dozen times, but . . . they're not fool proof.  Nothing is.  I don't know how many times I'd check the integrity of tape backups and find corrupt ones.

With that said, I don't have any formal backup routine at home.  My OS (along with the My Documents folders, etc.) is on a RAID 1 mirror, and all my media is on a cheap, 1.5 TB (effective) Buffalo Terastation.  I don't really trust the Terastation too terribly much.  It seems a little bit flaky.  If the power goes out and the UPS allows it's power to surge for a split second, it will spend the next 12 hours "resynching" the drives, during which time the performance is awful and streaming media from it frequently hiccups.  PITA.  I don't trust it to keep all my stuff 100% safe, but it brings my risk levels down to levels that I'm reasonably comfortable with, and I don't have to lift a finger for it so I'm pretty happy.  Anyway, 90% of the data on it is pirated so I technically have no right to it anyway.  Easy come, easy go.

boykster:

--- Quote from: shmokes on February 01, 2008, 11:13:15 pm ---I've seen a RAID 5 array refuse to rebuild itself after a drive failure and I've known at least two or three other people (professionals) who have personally had the same experience.  I've seen them rebuild just fine a dozen times, but . . . they're not fool proof.  Nothing is.  I don't know how many times I'd check the integrity of tape backups and find corrupt ones.

--- End quote ---

No strategy is perfect;  a few years ago, I had a software raid5 array completely go.  2 drives died simultaneously and that was that.  Last year, I had a hardware raid5 array suffer from some serious data corruption and loss.  One drive was getting kicked from the array for ata timeouts (benign problem, usually power related) but simultaneously I had a REAL hardware failure on a different drive but because the array was degraded, the controller was more conservative about kicking the real failed drive.  I couldn't rebuild the array because the bad drive would lock up before I could get the "good but kicked" drive back in the mix.  Because the array was still functional as long as the "bad" drive didn't freeze up, I was able to transfer about 80% of the data off.

My next system will probably be a larger array either in a RAID6 or RAID5 + hotspare setup....

squirrellydw:
OK, I understand raid 5 and 6 pretty well but what does the hotspare do?  I will probably use the adaptec card with a raid 6.

patrickl:

--- Quote from: boykster on February 01, 2008, 07:11:52 pm ---
--- Quote from: patrickl on February 01, 2008, 05:57:36 pm ---A big problem I still have is with backups. How do you backup 1.3TB?

--- End quote ---

As for the OS on the array or on another drive, its really a matter of personal preference.  If you're looking for high availability and low-downtime, you'd keep your OS on a seperate drive.  If the system crashes, you can easily move the entire array to another machine.  If the OS drive crashes, you can swap in a new drive and be back up an running (assuming you have a clean mirror copy of the OS sitting around like me  ;) ).

nothin wrong with putting the OS on the array, just not how I would do it.

--- End quote ---
Not trying to be argumentative her, but I really do not see why it makes it easier to move the array to another computer.

Why do you think it's easier or requires less maintenance to have the OS on another drive?

When I had a hardware RAID card I put the OS on a partition of the array. If I want to move the array to another computer it would have the OS on a drive already so I simply don't mount the OS partition of the array. A separate is practically a separate drive yet a partition is safeguarded by the RAID and a single drive is not. I don't see any advantage in a extra OS drive, what am I missing?

When you add an extra drive for the OS you actually add another point of failure. Even worse, you add another non-redundant point of failure.

boykster:

--- Quote from: squirrellydw on February 02, 2008, 03:16:12 am ---OK, I understand raid 5 and 6 pretty well but what does the hotspare do?  I will probably use the adaptec card with a raid 6.

--- End quote ---

A hotspare drive is just a drive "in waiting" in case a failure happens.  If a drive fails in a RAID array, rather than waiting for user intervention to swap out a bad drive, the hot spare is swapped in and hte array is rebuilt.  Its an additional (-1) in the whole scheme of things, and adds an additional level of "safety".


--- Quote from: patrickl on February 02, 2008, 03:27:12 am ---Not trying to be argumentative her, but I really do not see why it makes it easier to move the array to another computer.

Why do you think it's easier or requires less maintenance to have the OS on another drive?

--- End quote ---

seriously, if you want to put your OS on the array, then do it.  If you were building a scalable data center you wouldn't.  Its all about abstracting the "system" from the "storage".  I have 3 RAID5 arrays on 2 systems.  Depending on what computer has the RAID cards and drives installed, those arrays could live on any computer.  The OS and the storage arrays are independant. 

Its not that I don't consider the OS to be worthwhile to be redundant, its that I consider the OS to be a seperate entity.  In fact I keep a "bare metal" backup of 3 systems: one each for my storage machines and one for my applicaton server....

Navigation

[0] Message Index

[#] Next page

[*] Previous page

Go to full version