Re: Performance problem - reads slower than writes

Brian Candler
2012-02-03T21:17:44Z

On Fri, Feb 03, 2012 at 09:01:14PM +0000, Brian Candler wrote:
> I created a fresh filesystem (/dev/sdh), default parameters, but mounted it
> with inode64. Then I tar'd across my corpus of 100K files. Result: files
> are located close to the directories they belong to, and read performance
> zooms.

Although perversely, keeping all the inodes at one end of the disk does
increase throughput with random reads, and also under high concurrency loads
(for this corpus of ~65GB anyway, maybe not true for a full disk)

-- original results: defaults without inode64 --

#p files/sec dd_args
1 43.57 bs=1024k
1 43.29 bs=1024k [random]
2 51.27 bs=1024k
2 48.17 bs=1024k [random]
5 69.06 bs=1024k
5 63.41 bs=1024k [random]
10 83.77 bs=1024k
10 77.28 bs=1024k [random]

-- defaults with inode64 --

#p files/sec dd_args
1 138.20 bs=1024k
1 30.32 bs=1024k [random]
2 70.48 bs=1024k
2 27.25 bs=1024k [random]
5 61.21 bs=1024k
5 35.42 bs=1024k [random]
10 80.39 bs=1024k
10 45.17 bs=1024k [random]

Additionally, I see a noticeable boost in random read performance when using
-i size=1024 in conjunction with inode64, which I'd also like to understand:

-- inode64 *and* -i size=1024 --

#p files/sec dd_args
1 141.52 bs=1024k
1 38.95 bs=1024k [random]
2 67.28 bs=1024k
2 42.15 bs=1024k [random]
5 79.83 bs=1024k
5 57.76 bs=1024k [random]
10 86.85 bs=1024k
10 72.45 bs=1024k [random]

Regards,

Brian.