Disk subsystem throughput

As told earlier, I swiched from PCI RAID controller to RocketRaid 2320 PCI-E (x4) RAID controller. Throughput is up significally:

Read speed:

• Before 100 MB/s
• After 520 MB/s (UP 5,2 times)

Write speed (RAID-5)

• Before 54 MB/s
• After 150 MB/s (UP 2,8 times)

Important fact is, that using packets less than 8 MB gave > 1022 MB/s read/write speeds because of new cache employed on the new controller. I's PCI-E x4 physical limit !?

PCI-E RAID controller installed

Due to some compatibility issues I decided to get rid of old-fashined PCI RocketRaid 1820A and replace it with very modern PCI-Express technology RocketRaid 2320 unit. It has PCI-E x4 architecture.

My media server in the nutshell

• Dell PowerEdge SC1430
• Quad core Intel E5335 CPU 2,0 GHz, 1333MHz FSB, 2x4 MB L2 cache
• 2GB Memory
• HDD 80 GB dedicated to OS and programs
• RAID 5 2,25 TB (4x750 GB Hitachi SATA), dedicated to digital media
• RocetRaid 2320 RAID host adapter, PCI-E x4 (300 MB/s each SATA port)
• Broadcom Gigabit NIC

My main objective was to get away from compatibility issue, but once I had to reinstall my RAID, I choce more potent PCI-E model to get rid of all possible bottlenecks in the data path.

System bottleneck speeds:

So, network is the slowest link in the chain.

Half Terabyte server update

I downloaded best performance meter available -- Iometer. As the Iometer User's Guide says, Iometer is an I/O subsystem measurement and characterization tool for single and clustered systems. It was originally developed by the Intel Corporation and announced at the Intel Developers Forum (IDF) on February 17, 1998 - since then it got wide spread within the industry. Look more: www.iometer.org

So, I played in my home network, particularly with my HTMS (Half Terabyte Media Server) RAID subsystem.

My HTBMS server config:

• Dell Dimension 8200 base, 2GHz P4, 512MB RAM (tower)
• 4 PCI 33MHz x 32bit slots,PCI 2.2 compliance + AGP slot
• Intel PRO/1000 MT Gigabit NIC
• HighPoint RocketRAID 1640 SATA RAID conroller
• 4 x 160 GB SATA drives (WD + Seagate) in RAID 5 configuration
• MS Windows XP Pro
• TwonkyMedia UPnP media server

So, test data:
Maximum read throughput: 100 MB/s (with >1Mb packets)
Maximum write throughput: 10 MB/s
Maximum I/O ops/s: 10 000 ops/s (with 512 Kb packets)

I am not happy with write performance. Read performance is very good, also through gigabit NIC and my home lab, all gigabit. Problem for low write performance is parity calculation during write in RAID5 model. Option is to go for RAID 0 or 1, but I'd like to stay in RAID5, because of reliability and space. Buying model 1640 I didn't have any idea, that parity is calculated by computers CPU. So, processor load is 100% during large writes. I found that RocketRaid 1810a has hardware XOR parity module, so CPU is not overloaded. Have to swap RAID controller, or I'm not satified.

I found extremely interesting forum thread about buidling cheap and powerful RAID5. Must reading for everybody, who are trying it at home.