Re: What stripe size for mail server?
Ah, ok that changes everything. "mailboxes" ;)
At 12:30 AM 11/11/04 +0100, Marcin Owsiany wrote:
>> If u still need RAID 5 then I would make the stripe size equal to
>> average file size / number of data disks up to no more than 32KB stripe.
>
>Since avg file size would be something around 2500 bytes, and we have 5
>disks, that would give us a 500 byte stripe. I don't think that is even
>possible.
Since you (happy Adrian??) have lots of small essentially static files the
limiting factor will probably be the disk I/O. Optimizing for I/O is a
trade off for optimizing for non-wasteful disk usage. To bring down the
number of I/O's needed to get a file u want to make the stripe larger. But
making the stripe larger can slow down writes and waste space in the form of
"latent space". If u have 32KB stripes so that almost every file fits in 1
stripe, the leftover space is wasted. So a 2.5KB file written in a 32 KB
stripe wastes 30.5 KB. This could be ok if space is no object in the face
of fast I/O speed. Given how cheap hard disks are now it could be worth it
to err on the large side. The other caveat there is the
read-recompute-write cycle of a large stripe. Smaller stripes speed this
up. So all in all, for ur microscopic little files, I would make the stripe
4 KB. If ur having trouble with the stripe concept it is identical in
practical use to a cluster on a normal partition.
RAID:stripe::partition:cluster.
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