Some Unix benchmarks for those who are interesed

[Ivan Voras]

Artem Kuchin wrote:
> Hmm. what kind of HDD, RAID or whatever are you using?
> My raid pretty much sucks. It is build it on the intel motherboard
> LSI Megaraid. But i still get 81Mb/sec when doing
> dd if=/dev/ar0 of=/dev/null bs=1M
> 
> How much do you get on this?

geom_mirror on 2 desktop SATA drives, but the results of dd are pretty low:

# dd if=/dev/mirror/data of=/dev/null bs=1m count=1000
1000+0 records in
1000+0 records out
1048576000 bytes transferred in 17.817686 secs (58850290 bytes/sec)

As you can see, results with a single drive are better:

# dd if=/dev/ad4 of=/dev/null bs=1m count=1000
1000+0 records in
1000+0 records out
1048576000 bytes transferred in 16.219518 secs (64649023 bytes/sec)

The mirror algorithm is "split":

# gmirror list
Geom name: data
State: COMPLETE
Components: 2
Balance: split
Slice: 16384
Flags: NONE
GenID: 0
SyncID: 1
ID: 1455065622
Providers:
1. Name: mirror/data
   Mediasize: 249999999488 (233G)
   Sectorsize: 512
   Mode: r7w7e8
Consumers:
1. Name: ad4
   Mediasize: 250000000000 (233G)
   Sectorsize: 512
   Mode: r1w1e1
   State: ACTIVE
   Priority: 0
   Flags: DIRTY
   GenID: 0
   SyncID: 1
   ID: 2273811345
2. Name: ad6
   Mediasize: 250000000000 (233G)
   Sectorsize: 512
   Mode: r1w1e1
   State: ACTIVE
   Priority: 0
   Flags: DIRTY
   GenID: 0
   SyncID: 1
   ID: 926967552

Setting the algorithm back to "load" gives the performance similar to
that of a single drive:

# dd if=/dev/mirror/data of=/dev/null bs=1m count=1000
1000+0 records in
1000+0 records out
1048576000 bytes transferred in 16.551914 secs (63350740 bytes/sec)

It's really unusual that geom_mirror cannot benefit from splitting requests.

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