Text 27556, 159 rader
Skriven 2007-01-25 09:48:02 av Jeff Guerdat (1:229/2000)
     Kommentar till en text av Jeff Guerdat
Ärende: duo core - what for?
============================
Repost for Gerald...

Jeff Guerdat -> Gerald Miller wrote:
 JG> Gerald Miller wrote:

 >> So, there is the possibility that the forthcoming "screamer" will be an
 >> acceptable machine after I retire?  I am greatly relieved by that
 >> prospect.

 JG> Oh, yeah, mamma!  There's strength in the argument that you should just
 JG> get the cheapest machine you can and replace it every couple of years
 JG> (or as needed) but I prefer to have forward looking expansion capability
 JG> in the first place.  Obviously, "It depends" is a valid modifier.

 JG>>> Due to the CPU choice, it's also a nice space heater for the winter
 JG>>> months...  ;)

 >> Hummmm.  That's not the way I want to go!  I got seven fans -- four
 >> intake
 >> and three exhaust.  I had thought about going water cooled, but the price
 >> quickly modified my thinking.

 JG> It's primarily due to to the Xeon CPUs.  Nowadays I'd get a dual core
 JG> something-or-other and have the same benefit with lower power
 JG> consumption and, hence, less heat.  You no doubt have a superior system
 JG> (at least heat-wise) because you're buying current product.  Two years
 JG> ago, dual cores were still being discussed as the next great thing - I
 JG> didn't have a choice.

 JG>>> It does take a while to get all the little things converted (mine
 >> was
 JG>>> from SCSI to SATA) and to determine what the gotchas are so they can
 JG>>> be overcome.  For me, it boiled down to 1) getting multiple SATA
 JG>>> drives to allow the use of the built-in RAID controller and 2)
 >> memory.

 >> The RAID thingie has me a little confused.  The MB has Intel Matrix
 >> Storage
 >> Technology (RAID 0, 1, 10, 5) and after doing a search at the Wiki
 >> site for
 >> the different RAID "standards", I'm even more confused.

 >> I think it will be a while before the machine is online, so I will have
 >> some time to ask more questions about RAID and then make a decision.

 JG> The RAID levels are a bear to remember if you don't work with them.

 JG> RAID 0 is simple striping - you read or write something and the
 JG> controller splits the job between available drives.  With two drives,
 JG> you get nominally a 2x performance increase since each drive is writing
 JG> concurrently.  Three drives, like I have, gives you 3x the performance.
 JG>   You also get capacity multiplied by the number of drives.  However,
 JG> there's no redundancy so your data is at risk as much as with one drive
 JG> in a normal system.  You need a minimum of two drives.

 JG> RAID 1 is mirroring.  What you write on one disk gets written to the
 JG> second automatically.  You can forget about needing to clone a drive for
 JG> backups because it's done for you.  There's a slight performance gain
 JG> because the drive that's ready first is the one to respond.  However,
 JG> there's a loss of capacity since each drive is a duplicate of the other.
 JG>   You can have multiple drives in each part of the array but the $$$
 JG> overhead is 100% because you need the same number of drives for each
 JG> side of the mirror.  If one side dies, the other can pick up
 JG> automatically (depending on the controller) or you can do some quick
 JG> reconfiguring to do it manually.  Once the bad drive(s) is replaced,
 JG> rebuilding should happen automatically.  You need a minimum of two
 JG> drives but get only the capacity of one.

 JG> RAID 10 is generally a combination using BOTH striping (for performance)
 JG> and mirroring (for data protection).  Tends to be expensive due the
 JG> large number of drives needed (a minimum of four drives).

 JG> I prefer RAID 5 where striping is used but, like ECC memory, there's
 JG> parity information written.  Since the parity bit has to be written to
 JG> some drive, you effectively have however many data disks plus one.  The
 JG> parity information is actually written across all drives but the effect
 JG> is as if one drive held it all.  There's frequently a small performance
 JG> penalty since the parity information has to be generated and written.
 JG> This scheme will support a single bit (drive) problem.  There are newer
 JG> schemes that support at least 2 bit errors but then you need two extra
 JG> drives.  Minimum of three drives (two data, one parity).  Data is
 JG> automatically calculated with a failed drive so you keep on going but at
 JG> a reduced rate.  Upon replacement of the failed drive, data is
 JG> automatically written to the new drive to bring it up to the level of
 JG> the other drives.  There's also a performance loss during this process
 JG> due to the overhead of calculating the needed data and writing it but
 JG> once it's done, full performance returns.

 JG> And then there's hot spares, depending on the size and scope of your
 JG> RAID controller and hardware.  This is a nice to have, but expensive,
 JG> redundancy built in where an unused drive is automatically swapped in
 JG> (logically) for a failed drive.  It has no use other than to be ready in
 JG> case of failure.

 JG> Whew!

 JG> If you want performance and have some backup strategy to recover from a
 JG> failed disk, RAID 0 is the fastest and cheapest.  Not all cheap RAID
 JG> controllers support RAID 5 so you're left with RAID 0 for data
 JG> protection, which requires 2x the drives.  I chose performance over
 JG> reliability and have backups automatically run by writing to DVD+RW.  No
 JG> need to shut down to backup but there is disc swapping that occurs for
 JG> the full backups (I do full once a month and incrementals weekly).  Your
 JG> paranoia level should dictate your strategy.

 >> I have two Seagate 320GB SATA drives for the boot OS (both mounted in
 >> drive
 >> caddies so that the boot OS can be cloned)

 JG> Right now, you could use either RAID 0 (performance with bothe drives in
 JG> the stripe set) or RAID 1 (mirroring so that data is automatically
 JG> duplicated on both drives).

 >> If one drive in the array should fail, does the data on the remaining two
 >> become corrupt?

 JG> For RAID 0, yes.  For RAID 1 or 5, no, you're protected although still
 JG> subject to a possible loss of another drive.  Again, your own paranoia
 JG> level should dictate.

 >> I do like the aspect of the drive speed though...  <g>

 JG> Me, too!  That's why I use DVDs for backups with a true backup solution
 JG> so that backups can be run on a live filesystem - no need to shutdown or
 JG> otherwise halt work.  I have it run overnight so there's little to no
 JG> impact.  Full backups require disc swapping but I'm ok with that.

 >> I'll have to get back to you in regards to the memory.  I'm hoping
 >> that 4GB
 >> should be adequate but I see in another message that there may be some
 >> limitations on how the memory can be deplored.

 JG> Yup - you need the /3GB switch on the OS line in boot.ini or you're
 JG> limited to 2GB for applications.

 GM>>>> Now, if I can just keep my wife off the new machine (I'm giving her
 GM>>>> the Duron)...

 JG>>> I solved that by giving my wife a laptop.  Doesn't need to be fancy
 JG>>> for her needs.  (I actually think she's a bit intimidated by the
 JG>>> desktop machine - she rarely uses it...)  ;)

 >> Sorry, a laptop for the wife is not within the budget.

 JG> Well, there's some reasonably attractive pricing.  $500 or so should get
 JG> something useful - just postpone a few plans for the new desktop.  Yeah,
 JG> right, like *I* would ever do that...  <smirk>

 >> The other part of my plan is to transfer my DOS system from the 200MHz
 >> box
 >> to the 500MHz machine.  That should be a snap because on ocassions, I've
 >> had to swap the drive caddie from the 200 to the 500 box and
 >> everything was
 >> "peaches and cream", only faster.  <grin>

 JG> Ah, the simplicity (both positive and negative)...  ;)

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