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RAID 5 beats RAID 10

RAID 5 beats RAID 10

Can I get some feedback on these results? We were having some serious
IO issues according to PerfMon so I really pushed for RAID 10. The
results are not what I expected.

I have 2 identical servers.

Hardware:
PowerEdge 2850
2 dual core dual core Xeon 2800 MHz
4GB RAM
Controller Cards: Perc4/DC (2 arrays), Perc4e/Di (1 array)

PowerVault 220S
Each Array consisted of 6-300 GB drives.

Server 1 = Raid 10
3, 6-disk arrays

Server 2 = Raid 5 (~838 GB each)
3, 6-disk arrays (~1360 GB each)

Test Winner % Faster
SQL Server - Update RAID 5 13
Heavy ETL RAID 5 16
SQLIO - Rand Write RAID 10 40
SQLIO - Rand Read RAID 10 30
SQLIO - Seq Write RAID 5 15
SQLIO - Seq Read RAID 5 Mixed
Disktt - Seq Write RAID 5 18
Disktt - Seq Read RAID 5 2000
Disktt - Rand Read RAID 5 62
Pass Mark - mixed RAID 10 Varies
Pass Mark -
Simulate SQL Server RAID 5 1%

I have much more detail than this if anyone is interested.

May 1 '06 #1
13 15405
Are you absolutely absolutely absolutely sure the disk write cache on both
machines was set the same?

RAID 10 will always out perform RAID 5 on read performance in a real
situation because it has 2 copies of the data it can concurrently read. When
writing to disk RAID 5 needs to read as well in order to calculate parity.

There is just so much to doing the comparison....

--
Tony Rogerson
SQL Server MVP
http://sqlserverfaq.com - free video tutorials
"Dave" <da******@gmail .com> wrote in message
news:11******** **************@ g10g2000cwb.goo glegroups.com.. .
RAID 5 beats RAID 10

Can I get some feedback on these results? We were having some serious
IO issues according to PerfMon so I really pushed for RAID 10. The
results are not what I expected.

I have 2 identical servers.

Hardware:
PowerEdge 2850
2 dual core dual core Xeon 2800 MHz
4GB RAM
Controller Cards: Perc4/DC (2 arrays), Perc4e/Di (1 array)

PowerVault 220S
Each Array consisted of 6-300 GB drives.

Server 1 = Raid 10
3, 6-disk arrays

Server 2 = Raid 5 (~838 GB each)
3, 6-disk arrays (~1360 GB each)

Test Winner % Faster
SQL Server - Update RAID 5 13
Heavy ETL RAID 5 16
SQLIO - Rand Write RAID 10 40
SQLIO - Rand Read RAID 10 30
SQLIO - Seq Write RAID 5 15
SQLIO - Seq Read RAID 5 Mixed
Disktt - Seq Write RAID 5 18
Disktt - Seq Read RAID 5 2000
Disktt - Rand Read RAID 5 62
Pass Mark - mixed RAID 10 Varies
Pass Mark -
Simulate SQL Server RAID 5 1%

I have much more detail than this if anyone is interested.

May 1 '06 #2
All the arrays have the same settings

Read Cache: Adaptive Read Ahead
Write Cache: Write Back
Cache Policy: Cache I/O

May 1 '06 #3
If you are using Dell hardware with Perc controllers - Read this:

http://forums.2cpu.com/showpost.php?...6&postcount=11

I will be testing this during the next day to see if this explains my
overall bad diskperformance .
"Dave" <da******@gmail .com> wrote in message
news:11******** **************@ g10g2000cwb.goo glegroups.com.. .
RAID 5 beats RAID 10

Can I get some feedback on these results? We were having some serious
IO issues according to PerfMon so I really pushed for RAID 10. The
results are not what I expected.

I have 2 identical servers.

Hardware:
PowerEdge 2850
2 dual core dual core Xeon 2800 MHz
4GB RAM
Controller Cards: Perc4/DC (2 arrays), Perc4e/Di (1 array)

PowerVault 220S
Each Array consisted of 6-300 GB drives.

Server 1 = Raid 10
3, 6-disk arrays

Server 2 = Raid 5 (~838 GB each)
3, 6-disk arrays (~1360 GB each)

Test Winner % Faster
SQL Server - Update RAID 5 13
Heavy ETL RAID 5 16
SQLIO - Rand Write RAID 10 40
SQLIO - Rand Read RAID 10 30
SQLIO - Seq Write RAID 5 15
SQLIO - Seq Read RAID 5 Mixed
Disktt - Seq Write RAID 5 18
Disktt - Seq Read RAID 5 2000
Disktt - Rand Read RAID 5 62
Pass Mark - mixed RAID 10 Varies
Pass Mark -
Simulate SQL Server RAID 5 1%

I have much more detail than this if anyone is interested.

May 8 '06 #4
Per Schjetne wrote:
If you are using Dell hardware with Perc controllers - Read this:

http://forums.2cpu.com/showpost.php?...6&postcount=11

I will be testing this during the next day to see if this explains my
overall bad diskperformance .


I may be missing something but is "write back" not slower than "write
through" anyway? I mean with write through the data has to be written
twice with RAID 10 before the IO call returns; I'm not sure whether this
can happen in parallel - if not you're at twice the time. But with
write back the controller can put the data into its internal cache (as
long as there is space left), IO call can return and then it can writing
stuff in the background.

Regards

robert
May 8 '06 #5
I have the exact same situation. We had a PowerEdge 2800 with RAID 5,
when we got a new one I pushed hard for RAID 10, and then when I ran
performance tests for our database it turned out to be not quite as
good as the RAID 5.

May 10 '06 #6
I can confirm the same thing. We have 2 x PowerEdge 2800 with the disks on a
PowerVault 220S. I have reconfigured one of the servers to Raid 10 and the
diskperformance went slightly down. I used ATTO Disk Benchmark for testing.
I also run some test-procedures in SQL Server and it confirmed the same
thing.

"sql_server_use r" <ka*******@gmai l.com> wrote in message
news:11******** **************@ i39g2000cwa.goo glegroups.com.. .
I have the exact same situation. We had a PowerEdge 2800 with RAID 5,
when we got a new one I pushed hard for RAID 10, and then when I ran
performance tests for our database it turned out to be not quite as
good as the RAID 5.

May 12 '06 #7
In theory, should this happen? Does anyone know of any published
benchmarks that compare Raid 5 to Raid 10 while holding the number of
disks constant?

May 12 '06 #8
Dave, I feel you should read Kimberly L. Tripp's response more carefully.
Her response is quite to the point. The performance comparison is not based
on the same number of physical disks, it is based on the same drive
capacity, using the same physical drives, but different number of them. Of
course if measured by basing on the same number of physical drives, you will
get the performance number as you stated, but that is just not the way
currently used to assess the performance.

"Dave" <da******@gmail .com> wrote in message
news:11******** **************@ j73g2000cwa.goo glegroups.com.. .
In theory, should this happen? Does anyone know of any published
benchmarks that compare Raid 5 to Raid 10 while holding the number of
disks constant?

May 12 '06 #9
I understood her post, I just don' think that the "current way" is
a logical or scientific way to analyze Raid. I understand the fault
tolerance and Degradation/Rebuilding benefits of Raid 10. However, for
performance reasons alone, I it doesn't appear to be justified.

I admit my testing is inconclusive. I wish I had to opportunity to
conduct more tests and see how performance varies with the number of
disks in the array.

It would also be interesting to repeat the tests on different hardware.

May 12 '06 #10

This thread has been closed and replies have been disabled. Please start a new discussion.

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