Subject Re[2]: [FB 2.1] Firebird engine seems to slow down on high load without utilizing hardware
Author Alexey Kovyazin (ak)


Definetely you need to compare real life loads.

Alexey Kovyazin

среда, 13 апреля 2016г., 04:47 +03:00 от "thetrynn@... [firebird-support]" <>:


Hey Alexey,
thanks you for our input. I think what you say is correct, and we reviewed our disk setup again.
We are utilizing mechnical discs so it's kinda hard to compare SSD performance to them.
But they should provide enought IOPS for our load.

Unfortunatly we can't just switch to a single SSD, since we would loose replication and failover systems the SAN provides which is a critical demand for us. I'm afraid for now we have to stick with it, until we have some facts to proof that the SAN Setup is our limiting factor. And data is not should that for me currently.

On a sidenode, we do own a server with SSD setup, but in tests we couldn't get a noticable performance gain through increasement of IOs this way. (tests was generic and not real world load unfortunatly)

Best Regards,

---In, <ak@...> wrote :

Hi Patrick,

If you say that problem occurred recently, I would suggest you to check SAN disks health.

However, these values


system IOPS under load read: 100
>Average system IOPS under load write: 550
Restore IOPS read: 1700
Restore IOPS write: 250 are really, really low.
1700 IOPS for the database with 4k page means 6.8Mb/sec (in case of random reads).

I suggest to install a single SSD drive and check how it will work.
SSD IOPS looks like
  Random Read 4KB (QD=32) :   283.050 MB/s [ 69104.0 IOPS]
  Random Write 4KB (QD=32) :   213.837 MB/s [ 52206.2 IOPS]

From our optimization practice we found that if you need to optimize only the single instance of the database, the most cost effective way is to upgrade to SSD first, and only then fix other problems.

Alexey Kovyazin
IBSurgeon HQbird



recently we had some strange performance issues with our Firebird DB server.

On high load, our server started to slow down. Select and update SQL query times did go up by more than 500% on average,

but reaching unreasonable high execution times at worst case. (several minutes instead of < 1sec)

OIT/OAT/Next Transaction statistics was within 1000 the hole time

We were not able to messure any hardware limiting factor. Indeed, this system was running with only 8 cores at about 70% CPU usage on max. load.

We decided that this may be our problem since we experienced a similar problem at about 80% CPU load in the past.

So we upgraded the hardware. As expected, the CPU-load dropped to ~35% usage on max. load scenario.

But this did not solve the problem.

Same story for the harddisk system. The usage is not even near it's max capacity.

We also can't see any impact on the harddisk.

We'r kind of stuck with our ideas, because we have no idea what could be a potential bottleneck to the system.

Since the hardware doesn't show a limit, there have to be anything else - most likely firebird engine related that's limiting our system.

We would be very grateful if anyone can give us hints where we can search further.

Or someone has similar experiences to share with us.

Operating System: Windows Server 2003

Firebird: 2.1.5 Classic

Dedicated database server (VMWare)

CPU: 16 cores, each 2.4 GHz

RAM: 32 GB

About 14GB are used from OS and firebird processes under max load.

HDD: SAN Storage System

Average system IOPS under load read: 100

Average system IOPS under load write: 550

Backup Restore IOPS read: 1700

Backup Restore IOPS write: 250

SAN IPOS Limit (max): 3000

Firebird Config Settings, based on defaults

DefaultDbCachePages = 1024

LockMemSize = 134247728

LockHashSlots = 20011


size: about 45 GB

450 to 550 concurrent connections

Daily average of 65 transactions / second (peak should be higher)

FB_LOCK_PRINT (without any params) while system was slowing down (~4 days uptime).

I have to note, Firebird was not able to print the complete output (stats was not cropped by me)


Version: 16, Active owner:      0, Length: 134247728, Used: 82169316

Semmask: 0x0, Flags: 0x0001

Enqs: 4211018659, Converts: 10050437, Rejects: 9115488, Blocks: 105409192

Deadlock scans:   1049, Deadlocks:      0, Scan interval:  10

Acquires: 4723416170, Acquire blocks: 640857597, Spin count:   0

Mutex wait: 13.6%

Hash slots: 15077, Hash lengths (min/avg/max):    3/  12/  25

Remove node:      0, Insert queue:     36, Insert prior: 74815332

Owners (456): forward: 131316, backward: 14899392

Free owners (9): forward: 39711576, backward: 49867232

Free locks (42409): forward: 65924212, backward: 23319052

With best Regards,

Patrick Friessnegg

Synesc GmbH