Friday, March 26, 2010

RAID and SSD

I really need a new desktop machine. The current dilemma is between large,cheap mechanical HD or small, costly, SSD.
The second question is "to raid" or not "to raid".

Solid-state-device VS mechanical disks:
Typical windows usage is faster with SSD. Question remains, is there a good&cheap drive. The new generation from SanDisk (g3) claims the following numbers:
Average sequential (higher is better) and Random-access latency(smaller is better)
Read- 220MB/s ,write 120MB/s . 0.1-0.2 ms latency. cost: for 60,120GB for 229$,399$

Mechanical disks: Some numbers:
VelociRaptor VR150 ,10,000 rpm, 300GB 102MB/s , 7ms - ~200$
Segate Baddacuda ST3320613AS , 7200 rpm , 230GB - 99.2MB/s ,17.1ms - 50$

Conclusion: SSD is worth the money

Raid
There are two goals for Raid. One is performance , Second is fault-tolerance. For a desktop owner the first tends to be the only relevant goal. Let`s assume you have a budget of up to 2 HD`s.
Raid 0 - two striped disks. If a file contains 4 sections , disk one contains 1,3 . The other 2,4.
on mechanical/ssd disks: x2 sequential-read , x0.9 random-read



P.S. What does the SATA150/SATA300 Interface means?
This is the BUS speed. SATA150 supports up to 150MB/s . SATA300 (or SATA-II) supports up to 300MB/s.
Make sure that the SATA interface max throughput > HD max throughput .