Re: Is there something that could change blocksize on iSeries?

The block size in question seems more like it’s the read/write cache size.

IBM Storage is literally IBM Storage guys that are looking at disk
performance because V9K write times are 3.5 ms. IBM expects write times
closer to 0.5 ms. They are claiming the that “something” changed the block
size on Sept 16 and that the V9K can’t change the block size so the system
or application must have changed it.

It seems to me that the SAN would be the only thing that would change its
block size.

I’ve been on IBM midrange for 30 years and I don’t know of any way for the
system to change block (cache) size.



On Fri, Oct 11, 2019 at 5:13 PM Vernon Hamberg <vhamberg@xxxxxxxxxxxxxxx>
wrote:

I wonder, as well - I just did a quick google on "v9000 block size" -
one hit talked about block size on IBM i disk units is 520 bytes, while
V9000 they are 512 bytes.

Then there is something it called allocation size - we talk about memory
on IBM i being in blocks of 4096 bytes.

There is also something I don't remember the name, but the amount that
is read from disk - this is up to 128K, IIRC, on IBM i, and this is used
to reduce I/O by reading the largest "segment" one can.

All in all, that was a lot of words giving no direct answer!! Maybe
it'll trigger some memories.

Vern

On 10/11/2019 3:03 PM, Roberto José Etcheverry Romero wrote:

What do they call block size? You have your pools, your volumes, they use
extents, etc etc etc, but block size? sounds weird to me... specially in
such non-binary numbers...

On Fri, Oct 11, 2019 at 12:17 PM Steve McKay <samckay1@xxxxxxxxx> wrote:

V7R3 system

IBM Storage Support says that the blocksize on our V9000 was changed

from

60K to 90K. They further say that something on the iSeries changed the
blocksize and there is nothing on the V9K that could change the

blocksize.

Is there anything on the iSeries that can change blocksize?

Thanks,

Steve McKay
(205) 585-8424
samckay1@xxxxxxxxx
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