Re: number of global spares?

[Bill Davidsen <davidsen@tmr.com>]

Dan Stromberg wrote:

>On Sat, 2005-08-27 at 15:00 +1000, Daniel Pittman wrote:
>  
>
>>"Guy" <bugzilla@watkins-home.com> writes:
>>
>>[...]
>>
>>    
>>
>>>>I've been working on a RAID setup with dual RAID controllers and
>>>>three expansion boxes - 48 disks in all, including data, parity and
>>>>global spares.
>>>>        
>>>>
>>[...]
>>
>>    
>>
>>>>They don't feel that the storage has to be blazing fast, and 100% uptime
>>>>isn't paramount, however they very much do not want to lose their data.
>>>>
>>>>The filesystem will not be backed up - we simply don't have anything large
>>>>enough to back it up -to-, so if the some part of the storage solution
>>>>goes kerflooey, we're totally...  er...  out of luck, and they'll probably
>>>>be looking at me (the primary sysadmin on the storage configuration),
>>>>wondering why their data is gone.
>>>>        
>>>>
>>>RAID5, 6 or 1 is not data backup!  It is hardware redundancy!!
>>>Data loss or corruption can still occur with a RAID solution.  RAID won't
>>>help if someone fat fingers a "rm" command.
>>>Corruption of the filesystem can also cause major data loss, without a
>>>failed disk.
>>>
>>>If the data was lost, what would it cost to re-create it?
>>>Enough to buy a backup system?
>>>      
>>>
>>I absolutely agree with this.  When - and it is when, not if - the
>>content of this filesystem goes away, you will be rightly blamed for it.
>>
>>Invest the few thousand dollars in a good high capacity tape drive and
>>pay someone to change the tapes.  This will be worth it when the system
>>finally does fail in some nasty, unpredictable way!
>>    
>>
>
>I was on paternity leave when the solution was selected, but the guy
>with the grant money has been disinterested in backups from the
>beginning.
>
>The policy is going to be "your homedir will be backed up.  Your files
>under /data will not, unless you back them up yourself."
>
>My job is to work within that restriction, and possibly advise for
>backups, but nothing more.  The purchasing decision is not mine.
>
Clearly you have some input into it. I would suggest that you at least 
go on record (paper trail CYA) on the need for backup. If you can't get 
incrementals on whatever does the /home directories, at least you could 
suggest a DVD burner and regular backups. That is a tiny bump on the 
hardware budget, and small storage requirement. You could backup as many 
datasets as will fit on one DVD every day, oldest unsaved first. Then 
when it fails you will be the hero ;-)

-- 
bill davidsen <davidsen@tmr.com>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979