[XCSSA] NAS the VIA EPIA way

[X-otic Computer Systems of San Antonio]

On Tuesday 30 June 2009 04:54:30 am X-otic Computer Systems of San Antonio 
wrote:

[RAID-5 Speed w/B.Backed Cache + WbackCache]
> Hmmm that's a slippery slope :) RAID5 might be faster for a while, but
> you can still fill up the buffer on the RAID controller with a busy DB
> server. 

Yeah... That can be true on a DB server. Or a streaming media server too for 
that matter.

> We have seen random I/O still be a significant issue on a 
> RAID5 versus a RAID10. 

Yeah.. I'm more talking about just regular OS I/O. But you're right too if the 
server is being used as a streaming media (video) box.. the RAM would fill up 
(or empty out) very quickly waiting on I/O to/from RAID-5.

> but you will 
> likely never see a RAID5 performance like a RAID0 for random I/O.
> Sequential I/O, however, isn't near as bad on a RAID5.

Speaking of RAID I/O speed.. I've always wondered.. do you see much/any I/O 
speed degradation on RAID-10 over say pure RAID-0?  Or is it more a 
spindle-count issue?


> Among other things, with XFS you can 
> describe the underlying drive configuration and make sure it optimizes
> for it. So, in theory, a RAID5 might not be all that bad. But it sure
> does suck for ext3 with MySQL :/

Yeah.. What happened to the XFS support?  I heard that it was being tested.. 
and "possibly"targeted for RHEL 5 U3..?

Cliffy.. you still on list?


> That said, that's why we beat performance issues with our RAID10
> hammer. Multiple failures possible, and it's hella fast on both reads
> and writes. For some customers, simply moving from a 3 drive RAID5 to
> a 4 drive RAID10 was like night and day. Plus there's no parity to
> compute - in some cases, believe it or not, a RAID10 in software has
> been known to beat our a RAID10 hardware (the stats I saw were with a
> ton of drives on some magical Sun box though) and part of that may
> have been due to the lack of needing to XOR everything.

Yeah.. I can see that.



> LSI MegaRAID SATA 150-6. It's from 2004 I think. I believe it has 64MB
> of onboard cache (non-upgradable).

Hmm.. a little small.. 2004?  Not SATA-II then?
Ahh yeah... It's PCI-64 but only 150MB/sec (not 300).
A littel slow to put new 1TB SATA-II drives in.

Good chat.. looking forward to your presentation man.. send me some 
bullets/links/whatever as soon as you're able.

Tweeks