[CentOS] I need storage server advice

Tue May 6 21:20:16 UTC 2008
Jason <jason at jasonandjessi.com>

I just posted this on my website, oddly enough.   While you need to
really understand your storage requirements to make an informed choice
between hardware or software RAID, with quad core CPUs being as cheap as
they are it's hard to not make the argument for software.
This is just hdparm over an average of 5 runs each on very similar

5 disc SAS array with 136g 10k drives and a hardware controller

Timing cached reads: 13336 MB in 2.00 seconds = 6673.96 MB/sec
Timing buffered disk reads: 98 MB in 1.18 seconds = 83.31 MB/sec

4 disc RAID 5 with 3Ware 9650SE and 500g 7200RPM drives

Timing cached reads: 6576 MB in 2.00 seconds = 3293.08 MB/sec
Timing buffered disk reads: 448 MB in 3.00 seconds = 149.20 MB/sec

Single 500g 7200 RPM SATA drive

Timing cached reads: 14220 MB in 2.00 seconds = 7119.78 MB/sec
Timing buffered disk reads: 198 MB in 3.02 seconds = 65.51 MB/sec

6 500g 7200 RPM SATA drives in a software RAID 5 array

Timing cached reads: 14364 MB in 2.00 seconds = 7191.86 MB/sec
Timing buffered disk reads: 852 MB in 3.00 seconds = 283.64 MB/sec


Michael Semcheski wrote:
> On Tue, May 6, 2008 at 3:11 PM, Ed Morrison <edward.morrison at gmail.com
> <mailto:edward.morrison at gmail.com>> wrote:
>     Situation:
>     My current storage needs are approximately 1.5 TB annually.  This
>     will increase to about 3.5 TB annually over the next 5 years (rough
>     est.).  This box will just be a data archive and once it is full it
>     will only be used very infrequently if not used at all. Files are
>     small up to 10 MB but numerous.
> The solution I found best was to buy a 2U server that has 8*750GB disks,
> though they'd probably be 1TB today.  Put the disks into a RAID 5 or 6. 
> Using hardware RAID, divvy them up into one 50GB drive, and one really
> large drive.  Put the OS on the 50GB drive, mount the really big drive. 
> Now you have a 50GB drive and a 7*750-50 drive.  When you fill that up,
> just buy another 2U server.  When you do fill it up, the next one will
> be cheaper and or bigger.
> The keys to this type of setup are:
> 1) Don't buy storage you'll need next year today.  The best time to buy
> this kind of hardware is right before you need it.
> 2) Look at the overall cost per gigabyte.  That's the metric that drives
> things.
> 3) Understand your tolerance for downtime and data protection.  If you
> have another copy, or a backup, and its not mission critical data, its
> much cheaper not to waste disks on redundancy.
> We have tape backups of our systems, and factoring in the cost of tape
> and other costs, its still possible to get storage with a marginal cost
> below $1 / GB.  That includes a 3 year warranty, quad core processor,
> 4GB of RAM  which you can probably put to use elsewhere.
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