Slooooow Raid performance...

[appleguru1]

So, I've been running a 600GB raid0 array for a while now... 2x 320GB Seagate SATAII drives, connected to my C2D 2.33GHz MBP via an Expresscard SATA controller (Sil 3132).

That setup gave me very good performance; consistently above 140MB/s read and write.

Today I got in a 5 bay port multiplying SATA case, along with 4 new seagate 320GB drives... so now I have 6 drives total.

Doing a raid0 stripe across all 6 drives gives me around 112MB/s, though sometimes even slower... Adding drives to a Raid0 should speed it up, not slow it down!

A raid 10 (stripe and mirror, 3 drives in each striped set mirrored), gave a dismal ~55MB/s.

...Single bare drive performance is just over 79MB/s read and write.

I'm in the process of building a raid 5 (using Silicon Image's SATA RAID 5 Manager) to test its performance, but I'm not too hopeful...

The theoretical maximum for this setup is ~320MB/s, which I really shouldn't have any trouble hitting with 6 drives raid0'd. (This is the 2.5Gb/s limit of the express card slot... the SATA II limit for all hardware involved is 3Gb/s).... Even if for some strange reason the setup was defaulting to SATAI (and it shouldn't be... all hardware is SATAII compliant and all drives are jumpered to SATAII), I still should be getting 1.5Gb/s, or ~192MB/s.

Any ideas as to why I'm getting such crappy performance?

 

[deadpixels]

i cannot directly help you with the problem but you can compare your speeds with he ones in this link for a approximative comparison.

http://macapper.com/2007/08/04/review-benchmarks-esata2-macbook-pro/

 

[appleguru1]

I have a feeling I'm bumping into the (arbitrary?) 125MB/channel limit that appears to be on the card I'm using. Not sure where that's coming from, as SATAII is supposed to be 3Gb/s, but still:

http://www.sonnettech.com/product/tempo_sata_express34.html

(Different manufacturer.. same card: says there under tech specs, Data Transfer Rate: Up to 125 MB per second per port).

So, given this information, theoretically I should have 2 drives per SATA port to maximize performance (A setup like that should give me ~240MB/s).. Unfortunately I only have one port multiplying case, so one channel can only have one drive.

So, since the performance per channel is limited to 125MB/s, adding more than 2 drives to a channel wouldn't net me a performance gain (and may actually give me a hit), so... what I'll try next is a raid0 with 2 drives in the case on one channel, one drive on the other channel and a FW800 drive (It's a PATA drive, seems to max out at ~37MB/s by it self)... That 4 drive raid should, at least based on my calculations and real world testing, get me ~240MB/s, though I'm expecting more like 150MB/s... which would not be much better than my 2 drive SATA raid0 got me :/

I'm expecting this lower value b/c when I had a 6 drive raid it spanned both channels.. and still only got me ~120MB/s...)

We'll see soon though!

 

[appleguru1]

Alright, so that 4 drive setup gets me just under 150MB/s (149.7MB/s Write, 144.7MB/s read)... Hrm...

Seems like my best bet for performance is to run a single drive per channel on SATA coupled with a FW drive (or two), striped.. should get me ~170MB/s... Let me try pulling one of the drives and connecting it via USB2.... 8)

 

[appleguru1]

Throwing USB 2 in the mix doesn't help... speeds drop to 61.1MB/s Write, 71.0MB/s read (This is with one SATA drive on each SATA channel, one drive on FW800 and one drive on USB2).

Lets try a 3 drive setup now, which based on my data should give me the best performance I'm going to get with what I have available... 1 SATA drive direct connect per channel (nix the multiplier), and 1 FW800 drive... 3 drive raid0.

I'm predicting ~170MB/s.

 

[appleguru1]

3 drive raid0, 2x320GB SATA via independent channels and 1x 400GB PATA via FW800 gave me 117.5MB/s Write, 180.5MB/s read (Peak read during 1GB ram to disk write ~205MB/s... Peak Write ~129MB/s)

...Single drive in port multiplying case but otherwise same setup gave ~117.3MB/s Write, ~179.4MB/s Read)

Other drives in case, mounted (in case... 2 in raid 10, 1 as bare drive, 1 as part of raid0.. 1 unused) gives roughly the same speeds.

 

[appleguru1]

Sorry for spewing the boards with benchmarks... just want this to be somewhere on the net in case someone is looking for similar data

4 drive raid0, 2 SATA on one channel, 1 SATA on the other channel, and one via FW800 gives write performance of ~150MB/s (Burst to ~174MB/s) and read performance of ~145MB/s (Burst to ~178MB/s)

 

[jamerson9]

Thanks for the tests. The results seems to reinforces other peoples benchmarks with 3 drive raid 0. This is the first result I've seen with 4 drives. Doesn't seem to be worth going for more than a 2 drive raid 0, given the trade off between the improvement in performance and increased risk of drive failure.

Sorry for spewing the boards with benchmarks... just want this to be somewhere on the net in case someone is looking for similar data

4 drive raid0, 2 SATA on one channel, 1 SATA on the other channel, and one via FW800 gives write performance of ~150MB/s (Burst to ~174MB/s) and read performance of ~145MB/s (Burst to ~178MB/s)