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Re: Of SANS and IOS

Answer to self, now anyone that reads the list will know!

According to this excelent (introductory) site:


IOPs is a messure of the IO requests per second a device will give you.
In the FC-SAN context, this IOps are actually blocks read/writen (makes
sense, thats what i thought) to the device.

Another interesting part in the site, mentions how overall performance
is seldom a function only of the storage device, but clearly depends on
the application.

This means, for example, that if you make an Email delivery farm, the
IOPS youll need will depend on the performance capabilility of your farm
(the application being in this case an SMTP server cluster), which has
obvious limitations (such as possible incomming bandwidth on the said
cluster, the blocksize and innards of your filesystem) among certain
statistically aquired or estimated variables (average email size comes
to mind).

So, basically, estimate the blocks per second your applications will
require, and that will be your IOPS requirement. For example, one can
take the Email farm as an example, you will need an imap server as well,
thats a whole lot of read operations. Take you email size estimate, your
number of received mails, estimate your number of peak concurrent users
and add that to the IOPS you got for the SMTP. Thats your IOPS
requirement combined.

Makes sense....anyone sees an inconsitency here? please correct me!

here is another page:


This one is like a sales bid, but it has interesting points... like,
dont trust vendors that dont publish the blocksize that they used to
messure IOPS performance.... same goes for the throughput value....

I hope more ppl contribute to this email, its a subdocumented topic in
the OSS world (you wont find it -YET- in the LDP)....

El vie, 19-09-2003 a las 17:08, Alex Borges escribió:
> Anyone knows What The FARKS is that IOs unit the HP SAN folk keep
> talking about? Like in, yeah, this thing can take 2000 IOS per second.
> How many bytes is an IOs supposed to be? An IO==Device blocksize or WTF?
> It seems like most that have bought a SAN knows how many IOs it is
> worth, but noone knows what an IOs is (yeah, Input Output Operation)....
> I know how many Gbps i need, not how many IOs, how do i go from one to
> the other?
> My guess is that its the blocksize of the fs that i plan to use. If so,
> ican divide my X Gbps between 8 to get GBps, then between 4000 to get
> the blocks per seconds i need....would that map into IOS?
> Treacherous salesmen everywhere!
> Lex

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