[DRBD-user] Significant performance improvement!

Marcelo Azevedo marzevd at gmail.com
Thu Jun 19 21:28:58 CEST 2008

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

After placing the metadata on a different spindle (HD) , i was able to reach
almost close to native speed (1-2MB/s less)

with metadata internal i was reaching tops around half of the native speed
,  37MB/s~ :
 physical partition -> drbd -> ext3
63MB/s~ with physical partition -> ext3
61MB/s with  metadata  external, now this is true for another strong
machine .

This other machine has hardware RAID1 with two :
Cheetah T10 series,
146GB ,Serial Attached SCSI
Interface Speed: 3Gb/s
Spindle Rotation Speed: 15,000 RPM
Performance: 10K
on an IBM 2G Xeon server with 2 dual cpu packages , each cpu with 4 cores .
 4GB of ram
native speed  -hardware raid1 ->  physical partition -> ext3 is around
110MB/s ( still isn't this a bit slow for this HD ? )
hardware raid1 -> physical partition -> drbd -> ext3 - 101MB/s with
external metadata on a USB2 connected SATA HD 7,200 rpm

now this is the crazy part  - 8.3MB/s~ write speed ! with internal metadata
, and 150MB/s read speed..
this test was repeated with bonnie , iozone and dd , all showed around same
numbers ,
i mean why the huge jump from 8MB/s to 100MB/s when using external metadata
, and should this be STRESSED on the Docs or when starting the program that
putting the metadata on external media improves performance significantly?
, still i don't understand why i was able to reach only 8MB/s write speed on
this strong server , maybe because of the hardware raid1 underneath?

kernel reports for the raid controller :
Adaptec aacraid driver 1.1-5[2437]-mh4
ACPI: PCI Interrupt 0000:04:00.0[A] -> GSI 17 (level, low) -> IRQ 16
PCI: Setting latency timer of device 0000:04:00.0 to 64
AAC0: kernel 5.2-0[15411] Oct 11 2007
AAC0: monitor 5.2-0[15411]
AAC0: bios 5.2-0[15411]
AAC0: serial 402A183
AAC0: 64bit support enabled.
AAC0: 64 Bit DAC enabled
scsi0 : ServeRAID
  Vendor: ServeRA   Model: system            Rev: V1.0
  Type:   Direct-Access                      ANSI SCSI revision: 02
drbd ver 8.2.6 (api:86/proto:86-88)

at first i thought it was network performance issue , i benchmarked with
ipref and reached 990Mbit gigabit speed, then i monitored the line with
iptraf and saw  14MB/s tops writing speed on the drbd drive , and 50MB/s
tops when doing synchronization

so i tried on standalone mode , and saw it would go beyond 8MB/s with the
benchmark tools , so it clearly wasn't a network issue

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