Question: with the same number of physical drives, do I get better
performance with one large md-based drive, or do I get better
performance if I have several smaller md-based drives?
Situation: dual CPU, 4 drives (which I will set up as RAID-1 after being
terrorized by the anti-RAID-5 polemics included in the Debian distro of
mdadm).
I've two choices:
1. Allocate all the drive space into a single large partition, place
into a single RAID array (either 10 or 1 + LVM, a separate question).
2. Allocate each drive into several smaller partitions. Make each set of
smaller partitions into a separate RAID 1 array and use separate RAID md
drives for the various file systems.
Example use case:
While working other problems, I download a large torrent in the
background. The torrent writes to its own, separate file system called
/foo. If /foo is mounted on its own RAID 10 or 1-LVM array, will that
help or hinder overall system responsiveness?
It would seem a "no brainer" that giving each major filesystem its own
array would allow for better threading and responsiveness, but I'm
picking up hints in various piece of documentation that the performance
can be counter-intuitive. I've even considered the possibility of giving
/var and /usr separate RAID arrays (data vs. executables).
If an expert could chime in, I'd appreciate it a great deal.
--
Moshe Yudkowsky * moshe@xxxxxxxxx * www.pobox.com/~moshe
"There are more ways to skin a cat than nuking it from orbit
-- but it's the only way to be sure."
-- Eliezer Yudkowsky
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