building a RAID system

Alvin Oga alvin at Mail.Linux-Consulting.com
Thu Oct 9 03:52:39 EDT 2003


hi ya

On Wed, 8 Oct 2003, Trent Piepho wrote:

> On Wed, 8 Oct 2003, Mark Hahn wrote:
> > > 	- get those drives w/ 8MB buffer disk cache
> > 
> > what reason do you have to regard 8M as other than a useless
> > marketing feature?  I mean, the kenel has a cache that's 100x
> > bigger, and a lot faster.
> 
> I found a comparison of 8MB vs 2MB drives in a raid, though it's windows
> based and not that great:
> http://www.madshrimps.be/?action=getarticle&number=13&artpage=289&articID=69

i dont have much data between 2MB and 8MB ... just various people's
feedback ...
	- releasable data i do have is at
	http://www.Linux-1U.net/Disks/Tests/
 
- testing for 2MB and 8MB should be done on the same system  of the
  same sized disks and exact same partition, distro, patchlevel and "test
  programs to amplify the differences"
	- lots of disk writes and reads ... that overflow the memory
	so that disk access is forced ...

> Seems like the 8MB didn't really make much of a difference.
> 
> > > independent of which raid system is built, you wil need 2 or 3
> > > more backup systems to backup your Terabyte sized raid systems

-- emphasizing .. "Terabyte" sized disk subsystems

> > backup is hard.  you can get 160 or 200G tapes, but they're almost 
> > as expensive as IDE disks, not to mention the little matter of a 
> 
> 100GB LTO tapes can be had for $36, that's less than half the price of the
> cheapest 200 GB drives. 

we/i like to build systems that backup 1TB or 2TB per 1U server ...
 	- tapes doesn't come close ... different ballpark 

	- a rack of 1U servers is a minimum of 40TB - 80TB of data ..

	- and than to turn around and simulate a disk crash
	and restore from backups from bare metal   or how fast
	to get a replacement system back online ( hot swap - live backups)

	- i think those 200GB tape drives is something to also
	add into the costs of backup media  .. as are restore
	from tape considerations  before deciding on tape vs disk 
	backup media ( all depends on the purpose of the server and data )

	- last i played with tape drives was those $3K - $4K exabyte tape
	drives ... nice and fast (writing) ..  but very slow for 
	restore and unreliable ... and time consuming and NOT automated

	- people costs the mosts for doing proper backups ... 
	( someone has to write the backup methodology ro swap the tapes 
	etc )

fries ( a local pc store here ) had 160GB disks 8MB buffers for $80 after
rebates ... otherwise general rule is $1 per GB of raw disk storage per
disk

fun stuff ..

have fun
alvin

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