Backup Server RAID Suggestions - Resend

[Bill Davidsen]

Gilboa Davara wrote:
> On Mon, 2008-09-08 at 06:35 -0700, Mike McMullen wrote:
>> Hi All,
>>
>> I am trying to build a NAS server based on Fedora 9.
>>
>> I will be using a de-branded HP Athlon 64 X2 Dual-Core with 2GB RAM and
>> two 250GB drives mirrored for the OS stuff and a few apps.

That's a bit light on RAM.
> 
> Depending on your usage case (random/sequential) I'd consider adding
> additional memory.
> 
>> I would like to add some type of raid storage box to it with about 5 1TB
>> drives using raid 5 unless there is something better.

I like software RAID6 (runs with any two drives failed), and you want to 
look at eSATA connection to an external box. Newegg has enclosures, as 
do many others.
> 
> I'd consider switching the 1TB drives with smaller one.
> IME big drives are (far) less reliable than small ones.

Today the values of big and smaller are changing every few months. What 
you say is generally true, although I find the new drives in general are 
better each upgrade.
> 
>> I want to use the system for photography work flow and backing up a few
>> Windows systems.
>>
>> My questions are as follows:
>>
>> 1. What is an inexpensive external RAID storage box to go with?
> 
> If you're talking about 5-8 drives, a big tower case will do.
> Any particular reason why your rather use an external case? (With an
> additional power supply?)

You want a big power supply and lots of fans. Drives don't like heat. 
Google released a paper on the relation between SMART monitoring and 
failure prediction, but it talks about some additional factors like heat 
and crappy power.
> 
>> 2. What is a good inexpensive RAID controller to go with?
> 
> 3ware has a very good SATA raid controller.
> Same goes for LSI.

And Adaptek. For software RAID you just use the JBOD mode.
> 
>> 3. S/W RAID vs HW RAID? Which is the most reliable way to go?
> 
> Hardware RAIDs are easier to setup and maintain, but cannot be
> transferred from one machine to the other.
> Expensive hardware RAID controllers add additional battery back cache
> that can improve the performance and reliability in case of power
> outage.
> 
> Software RAIDs are somewhat harder to manage, but can be moved from one
> machine to the other with no additional effort.
> Plus, software RAID has build in RAID6 support. (In case you need better
> reliability.)
> 
With software RAID you have a chance to talk to users and developers if 
you have some really odd problem, and it's part of Linux. Depending on 
the controller vendor you might not want to admit running Linux at all, 
and you surely won't get a patch. HW is easier to set up, just plug and 
pray.
> 
>> 4. Are there ways to do full backups of windows boxes and restore a
>> complete bootable drive from the Linux box?
> 
> Previous versions of Norton Ghost had no problems connecting to my samba
> shares.

And most systems can boot from a USB (and maybe eSATA) device.
> 
>> 5. What is the largest file system Fedora 9 can support?
> 
> ext3 is more than enough. (2TB file, 8TB FS)

Agree.
> 
>> 6. Are there performance hits for large file systems?
> 
> I'm using >1TB FS without a problem.

The only trick there is in defining your filesystem, I would use ext3 
because it is far more used and beaten upon, and your load sounds small. 
You want to be sure you use the optional parameter to match the RAID 
chunk size with the stride side, sparse superblocks, and hash 
directories if you will have a lot of smaller files in a directory.
> 
>> Thanks so much in advance!
>>
>> Mike
> 
> In general, I'd consider using ~11x500GB in a software RAID6 and put the
> OS on the same RAID. (10+1 setup)
> A CoolerMaster Stacker STC-101 case is more than capable of hosting >11
> 3.5" drives.

I would put the OS internally, since he has the existing drives for 
RAID1. Small drives would be faster, large drives cheaper per TB, and 
less heat per TB. I'll pass on reliability, smaller drives (using same 
technology) may be better, but you use more of them, so 500GB vs. 1TB 
the small ones need to be 2x better to have the same failure rate per 
TB. I have no insight into that, for power savings I usually go big.

Last thought: ship drives via UPS, I'm up to about 65 Seagates w/o a DOA 
with them, two for seven DOA with another popular shipper. It may be 
just my local people, but it's noticeable. A local PC clone dealer told 
me that many of the DOA drives were from shipping, and some distributors 
packed better than others.

Hope this helps. The linux-raid groups is very helpful, should you need 
help.
> 
> - Gilboa
> 
> 


-- 
Bill Davidsen <davidsen at tmr.com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot