From: centos-bounces@xxxxxxxxxx
[mailto:centos-bounces@xxxxxxxxxx] On Behalf Of Feizhou
>
> >> Another route you can go is getting a PCI/PCIe/PCI-X BBU
> >> RAM/NVRAM card
> >> to put an external journal on to speed up fsync performance for
> >> filesystems like ext3 over software raid since these cards
> >> can go beyond
> >> 1GB of memory unlike hardware raid cards that usually max out
> >> at 256MB.
> >
> > What are some of these BBU NVRAM cards that I keep hearing people
> > talk about? I would love to check them out.
>
> http://www.umem.com/Umem_NVRAM_Cards.html
> http://www.gigabyte.com.tw/Products/Storage/Products_Overview.
> aspx?ProductID=2180
>
> Weird...I thought the umem cards were more than just BBU
> SDRAM but...hmm...
Thanks, I'll have to give those bad boys a look-at.
> >
> >> Software RAID is also good if you need to be able to transfer
> >> the disks
> >> to another box that does not have a hardware raid controller
> >> or the same
> >> controller.
> >>
> >> Weigh these in your decision. :-)
> >
> > For 2 SATA hard disks used for the OS I think HW RAID is overkill.
>
> Depends. HW RAID + BBU CACHE vs SW RAID vs SW RAID +
> NVRAM...You cannot
> say overkill in certain cases.
I only say that because if one is really looking for high performance
then more spindles then 2 will be the first thing to do and getting
that data off the OS drives that may do swap under load is key too.
> >
> > Besides I do not believe the PERC 5IR has BBU cache, that
> > controller is really only meant as a simple RAID1 controller for
> > the OS.
>
> Dell certainly has a BBU cache option, not sure if OP's Poweredge box
> has that option.
Oh yes, the PERC 5e is very good, I have a couple here and they really
do pull in impressive numbers even with only 256MB write-back, I of
course use these with the MD1000 enclosures though.
> >
> > If you use HW RAID you will need to install the manufacturer's
> > software for monitoring it for a hard disk failure.
>
> Yes, likely a negative but with Dell supporting Linux maybe not so.
Ah, well a lot of these are Java apps for cross-platform compatibility
and some times the JavaVMs leak memory... so definitely YMMV.
> >
> > If you wanted to add additional storage, say a SAS/SATA enclosure
> > of 15 disks, then I would definitely invest in a HW RAID card for
> > that!
> >
>
> Depends :-D. How many hardware RAID cards offer 1GB of cache?
Not many I can tell you that, but then again a well implemented
write-back cache doesn't need a huge amount of memory to be effective.
-Ross
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