🚀 go-pugleaf

In article <40qs2d$5o9@news.cloud9.net>, tls@cloud9.net (Thor Lancelot Simon) writes:
|> In article <40qgii$nj8@sv01a.cis.squared.com>,
|> Tony Gast <cis115@ws001a.cis.squared.com> wrote:
|> 
|> (please restrict yourself to lines of 78 characters or less in the future 
|> -- please!)

Sorry, I reset my wrapmargin ...

|> 
|> Of course the cache increases read performance -- if you're reading data 
|> which is already in the cache.  But adding memory to the machine the disk 
|> is on will have exactly the same effect, and is much cheaper, too.
|> 

The vast majority of the data we access, and I believe this is a definite
industry trend, is in raw partitions being accessed by Sybase (Oracle,
Informix, what have you).  The OS does not cache this info.

|> You are unquestionably incorrect about StorComp's write caching.  It's a 
|> simple fact -- either the buffer cache and the filesystem knows about the 
|> write caching, or you can and likely _will_ lose the structure of the 
|> filesystem itself on a power hit.  If you're going to teach the 
|> filesystem code about the caching which the StorComp box does, you might 
|> as well just ditch the cache on the box alltogether -- again, main memory 
|> for the computer attached to the disks is cheaper anyway, and it probably 
|> isn't any harder to just make _it_ write in multiples of the stripe size 
|> than it is to make it understand that the StorComp box lies about write 
|> completion.
|> 
|> And without the write caching, the StorComp box is just like anyone 
|> else's RAID 4.  Except that it costs more, and that StorComp advertise it 
|> in inappropriate Usenet newsgroups, which is rude.

Posting to every group that might have people that have AS/400s with that
info is not great, however this peaked our curiosity as to whether IBM would
service RAID 7 for the RS/6000s now, and they do.  Granted, it would have
been more clever of StorComp to contact us directly ...

|> 
|> Heavens, no.  Auspex does a perfectly good job of selling their fileservers
|> themselves.  Just for reference, do you know what an Auspex is?  They're 
|> specialized network file servers which can cost millions of dollars.  They
|> also happen to use a correct RAID implementation which does write caching 
|> without running the risk of losing the whole filesystem.
|> 

I recall seeing Auspex advertised.  This sounds even more costly to have
such a specialized machine, but I am sure there are companies that need
exactly this sort of dedicated device.

We also happen to have switch gear that pulls power from two different
points (our local airport and a local hospital) as well as a backup deisel
generator that kicks into stand-by if either source drops below a certain
voltage, and a room o' batteries to carry or ES/9000 and all other systems
until the generator is fully on line.  I am at much higher risk of losing a
power supply in an RS/6K than losing multiple power supplies in the StorComp
box that would cause data loss.  Anyway, as with any technology that is not
a commodity yet, everyone will have to decide on whatever RAID-like product
suits their needs.  Just two more quick notes:
	The NVRAM is inexpensive to add
	You can put any SCSI drives into StorComp's boxes, so after the
		initial investment, adding capacity is much cheaper than 
		most other RAID vendors that require you use special magic 
		disks you can only get from them

Yet, no product is the right solution for everybody, and despite wanting to
live in a world where everyone knew enough about what they were buying not
to be burnt by filesystem corruption in general, we don't.  Because of this,
I believe your posts to be of greater general benefit than any marketing
type's ...
-- 
Reply-To: gasta@mcrsv001.squared.com
Tony Gast			(606)344-4528x4667
Square D Co.
Sr. UNIX Systems Administrator (Guy, dude, etc)