I just ordered a Promise s150 SX4 SATA RAID card and 4x 200GB hard
drive.  It's mainly going to be used as a file server.  Here's my
question.  I was thinking about what allocation unit size I was going
to use and I really need to use 2 different size.  I do a lot of video
work and take digital pictures at 5+ MP, so going with anything less
the 64Kb just doesn't make sense, but neither does allocating 64Kb for
my tons and tons of small files either.  So can I partition my drives
and format 1 partion for 4Kb and the other partition for 64Kb on each
of the drives?  I'll rarely be writing to both partitions at the same
time, so I don't have performance concerns, I just need to know if it
can be done.  I'm thinking it can't because of the BOIS config for the
card, but I may just be missing something.

Thanks,
snekse

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From what I know, allocation unit size is a concern of the filesystem and
not of the RAID. This is a command-line parameter to FORMAT or "newfs", depe
nds
on your OS.

--
Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
maxim@storagecraft.com
http://www.storagecraft.com

<snekse@hotmail.com> wrote in message
news:1103257111.146054.285790@f14g2000cwb.googlegroups.com...
> I just ordered a Promise s150 SX4 SATA RAID card and 4x 200GB hard
> drive.  It's mainly going to be used as a file server.  Here's my
> question.  I was thinking about what allocation unit size I was going
> to use and I really need to use 2 different size.  I do a lot of video
> work and take digital pictures at 5+ MP, so going with anything less
> the 64Kb just doesn't make sense, but neither does allocating 64Kb for
> my tons and tons of small files either.  So can I partition my drives
> and format 1 partion for 4Kb and the other partition for 64Kb on each
> of the drives?  I'll rarely be writing to both partitions at the same
> time, so I don't have performance concerns, I just need to know if it
> can be done.  I'm thinking it can't because of the BOIS config for the
> card, but I may just be missing something.
>
> Thanks,
> snekse
>

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On Fri, 17 Dec 2004 17:39:07 +0300, "Maxim S. Shatskih"
<maxim@storagecraft.com> wrote:

>    From what I know, allocation unit size is a concern of the filesystem a
nd
>not of the RAID. This is a command-line parameter to FORMAT or "newfs", dep
ends
>on your OS.

Yeah, but there's also stripe size to worry about!

(It may or -- usually -- may not make sense, for example, to have the
stripe unit smaller than the allocation unit).

Malc.

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Hi Malc,

Correct me if i am wrong. Are you talking of creating two RAID groups [
One group with stripe size of 4 kb and another group with stripe size
of 64 kb ]. You just have 4 harddisks right, and you need minimum 2
harddisks to combine to achieve any RAID level. This is the case, your
RAID5 configuration does not do much. You effectively loose 2 disks,
one in each group.

Pras

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On 22 Dec 2004 05:39:22 -0800, "pras" <msd.prasad@gmail.com> wrote:

>Hi Malc,
>
>Correct me if i am wrong. Are you talking of creating two RAID groups [
>One group with stripe size of 4 kb and another group with stripe size
>of 64 kb ].

No.

> You just have 4 harddisks right, and you need minimum 2
>harddisks to combine to achieve any RAID level. This is the case, your
>RAID5 configuration does not do much. You effectively loose 2 disks,
>one in each group.

So don't do it.  The question concerned the "correct" allocation unit
size , which Maxim pointed out was a function of the filesystem.  I
just pointed out the connection between the filesystem allocation unit
and the RAID stripe size.

The original poster will have decide which file size pattern they want
to favor, and go from there.  Which is, of course, always the case!

>Pras

Malc.

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