Raid 0 performance loss?

[wemmington]

How can I tell what stripe size I used for my raid 0 config? The reason I ask is I seem to have lost performance with my 2 120g seagate sata drives compared to my 120g seagate ide drive. I thought I set
the stripe size to 128 but when I defrag it says cluster size 4. Is cluster size same as stripe size? I dont know what else would have cuased a performance loss. Also I went with Intel raid, should I have used Promise? Thanks in advance for any help.

 

[SYAR2003]

Hi !
Cluster size is the default NTFS cluster , when partition was made/formatted , that is default 4k .

Btw ,it seems that there is agreed that this is really not good for a RAID 0 setup.

Stripe size is the divider of the files to save them
across the array (over the two disks ) .
E.g a stripe size of 128k will only use one disk
for all files lower in size , hence no performance boost.

All readings i have done about raid 0 recommends either 16 or 32k for the stripe size .

It seems to be depending on wich controller thats used
witch one that's best.

But if having the OS installed on that array
16k stripe size is supposed to give very good performance
and the NTFS should be partitioned with 16k cluster size.


Hope this sched some light on the matter of clusters and stripe sizes.

syar

 

[SYAR2003]

Hi again .
This will possibly explain the RAID 0 performance for OS .
Effect of striping files over two disks.

I have a reletive new install of win-xp on C:\ with NTFS
Only OS , office ,power-dvd , Nero , vpn-client is installed on this partition .
Three users with user data and dirs.

The total c:\ has 14080 files and directories .
Size of the files grouped
Directories = 1000
0-4kb size = 3660
5-8kb size = 1300
9-16kb size = 1240
17-32kb size = 1450
33-64kb size = 1690
65-128kb size = 1420
129-1024kb size = 2000
1025 and bigger = 320
The majority of files is 16kb or less.
So a 128k stripe will effect 2320 files in c:129kb-1024kb + 1025kb and bigger

While a 8k stripe will effect 8120 files in c:9-16 + 17-32 + 33-64 + 65-128 +129-1024 + 1025 and bigger


The total of c:\windows folder has 9800 files
Size of the files grouped
00-16kb size = 4500
17-32kb size = 1340
33-64kb size = 1700
65-128kb size = 500
129-1024kb size = 1560
1025 and bigger = 200
The majority of files is 16kb or less.
So a 128k stripe will effect 1760 files in this dir
129kb-1024kb + 1025kb and bigger)(


syar

 

[jurgen36]

In respect to raid 0. I use raid 0 with a cluster size of 32 Kb. My drives are formated with fat 32. The Sisoft readings are 82.352 MB/sec. The drives are Maxtors ata 133. I tested the array in NTSF formating and found that the readings dropped to 48.143 MB/sec. I can not explain this as NTSF should actually be faster. My second array also uses fat 32 but has a much higher speed as it uses SATA 150 drives. The sisoft readings are 93.243. However formated as NTSF the reading drops to 61.769 MB/sec. I hope this might help you. Incidently all drives are 80 GByte Maxtor drives. The two raid controllers are SIL and ITE build into the MBO. Greetings Jurgen

 

[jurgen36]

Some follow up. I used at first seagate drives in my raid system but had extremely low performance. Sisoft readings were lower as using a single drive. If I remember it was about 38 MB/sec. I returned the 8 drives to the shop and changed to maxtors and the speed went up drastically. I believe from other posts that many people have the same problem. Greetings Jurgen

 

[wemmington]

Thanks for all the replies. I changed the cluster size from 4 to 64 and my read/write went from about 38/43 to 69/77. Very happy with results! thanks again Bill