Any IDE RAID experts? What is the cache 4 on RAID cards?

[computer]

I've spent enough wasted hours on this and now have to ask the IDE RAID experts.

For ATA100/133 IDE RAID:
I've heard 32k cluster size is a bit large, 16k is more desirable and all the P4 boards w/integrated RAID are fixed @32k and cannot be altered. Is that true, they cannot be changed? I also cannot find out if integrated mobo RAID uses a buffer or not, can anyone answer that?

Is it best to use a PCI RAID card instead of integrated mobo RAID?

What are the disadvantage/advantage of having a buffer and the disadvantage/advantage of NOT having a buffer on PCI IDE RAID cards?

(I know what a cache/buffer is) but what EXACTLY does the buffer do on a RAID card and is it really needed?

Do these RAID card buffer sizes take precedence over the large 2mb to 8mb buffer sizes on IDE hard drives, as in; does this render the large HD buffers useless? IF this is the case, then I would think it would not be desirable to get a RAID card with a buffer.

This question of RAID buffers only recently presented itself with me when I noticed these Silicon Image ATA133 RAID cards I have, have a 128k buffer. I asked Promise if their cards have buffers or not, and they replied that the only one of their RAID cards that has a buffer is the SX6000, the rest do NOT.

The Silicone Image cards are here . Are these a POS, or are they pretty decent? (Note they have the 128k buffer).

I did find in my reading the Iwill SIDE RAID100 was the best software RAID 0 card, but cannot find out if it has a buffer or not.

Regarding cluster sizes for RAID 0:
Which is the best for PC use that includes......
12-14 hrs DAILY use
TONS of email (receiving and replying to ~400 emails a day) with OE.
TONS of web surfing with as many as 20 webpages open at once
Website design and maintenance incl. image editing
NO digital video/audio editing or ripping
NO gaming

Thanks for any replies.

 

[vetteguy]

What type of RAID are you wanting to do? 0? 1? I am actually curious about some of these issues myself, as I just put together a new RAID 5 system with 6 WD special edition 80GB drives. If you've got a fast processor the onboard should be ok, but I'm curious why you need RAID if all you're doing is e-mailing, web browsing and web design. None of those things are really HD intensive, and I don't think you'd gain anything by a RAID 0 setup (unless you want to do 1 for redundancy).

 

[Armitage]

IMHO, 128K of cache on a controller card isn't going to mean sqat. It's just trivial. SCSI RAID cards that have cache are ussually in the 10s to hundreds of MB. I'd be interested in benchmarks to prove otherwise, but I don't think 128K is going to do anything for you.

In general, the software IDE RAID cards aren't good for much beyond some improvement in RAID0, which is very risky. I went with 3ware myself, hardware based, well supported under Linux, and a nice read speed boost under RAID1..

 

[vetteguy]

Originally posted by: ergeorge
IMHO, 128K of cache on a controller card isn't going to mean sqat. It's just trivial. SCSI RAID cards that have cache are ussually in the 10s to hundreds of MB. I'd be interested in benchmarks to prove otherwise, but I don't think 128K is going to do anything for you.

Are you talking cache or stripe size here? I don't know of any RAID controller that has 128k of cache, my Promise SX6000 has 128MB of cache (it has a DIMM slot so you can put in as much as you want, up to 128). Is this what you're talking about?

 

[computer]

Yes, sorry it's RAID 0.

That was also another question, do I *really* need RAID. I currently use it (RAID 0, w/2 - Maxtor D740X ATA133, 7200, 2mb) on an Aopen AX37 Plus (integrated RAID).....and the only thing I really notice is I never have to defrag like I used to. I use to have to defrag every two weeks or so, now I can go over a month and it still only takes a few minutes. Evidently, RAID 0 drastically cuts down on fragmentation since half the data is going to the other drive. It's really hard to say though if it's any faster than a single drive since I have no way of comparing that in actual use without an identical PC to compare it to. The extensive write up at anandtech showed that in RAID 0, there was VERY LITTLE difference between a single drive and the best, fastest PCI RAID card.

Hell, I may just use my new WD800JB as a single drive on my old Promise Ultra100TX2 controller card. That way I'll still have separate IDE ports for each drive and won't have to do any 'slaving'. Or, use any integrated RAID on a new P4 board just as a regular IDE port. Which, brings up another question: is there any performance difference between an ATA100 IDE port, and an integrated ATA100 RAID port used as a regular IDE port?

 

[vetteguy]

Originally posted by: computerThat was also another question, do I *really* need RAID.

No, not for what you're doing.

Which, brings up another question: is there any performance difference between an ATA100 IDE port, and an integrated ATA100 RAID port used as a regular IDE port?

I don't think so, as long as you can disable the RAID functionality and use it as an IDE port. But why do you only want 1 IDE drive per port? How many drives do you have? The "slaving" issue isn't an issue at all, just takes a second to switch jumpers.

 

[computer]

Vetteguy; No, it's 128k buffer/cache on the card itself, not stripe cluster size. See the link above...
Two Ultra ATA Channels w/ 128 Bytes buffer per Channel
Looking at the card here, it has no provision for any extra RAM. I would guess that on software RAID cards you cannot add extra cache, but on hardware RAID cards, you can. ?

George; but is the 128k cache going to HURT anything? Will that take precedence over the 8mb cache on a WD800JB and render it useless, giving the hard drive instead only a 128k buffer?

Thanks guys.

 

[AncientPC]

AFAIK onboard RAID controllers are software and not hardware, offloading most of the algorithm processing to the CPU anyways (unless explicitly stated otherwise).

 

[vetteguy]

Whoops...sorry, didn't see the link. Most hardware RAID cards have RAM slots where you can add memory, but I have no experience with onboard, but I would assume that you can't add more to them. Sorry I don't know more!

Edit: I guess I should say most hardware RAID 5 cards, as those are the more heavy-duty ones.

 

[computer]

Yeah, I figure that's how is was. Now if I can only figure what that cache is for on that software RAID card and if it "defeats" the cache on a hard drive.

 

[computer]

Bump to find out about cache on RAID cards.....