RAID Question.

[Clunk]

Does anyone know how much impact the physical cache on the hard drive itself has on a RAID 0 setup?

I'm interested to know if anyone has done, or can point me in the direction of some tests that compare say, 2mb, 8mb, 16mb, 32mb cache drives in RAID 0.

Possibly RAID 5 as well.

Or, in a hardware RAID setup, is the RAID controller's cache more important?

Thnaks

[alsenior]

In a raid 5 controller the cache can be very important on the card. the cache on the drives themselves can be useful and it is useful t have it. but a decent hardware controller can give better performance, not to mention the ability to change motherboards without having to reinstall every thing.

Edit: i don't think i could recommend anyone use raid 0 especially with drives being so cheap at the moment

[Jay]

I use RAID 0 but only because I can.... I don't need to and to be honest its not the best idea!

Get a decent 750gig single drive and you will be flying, I would stay away from RAID 0 if I was you.

[Clunk]

Thanks mate

The controller card has RAID levels 0, 1, 1E, 5, 5EE, 6, 10, 50, 60, JBOD.

Was looking at raid 5 as well, but there seems to be a fair drop in performance compared to raid 0 (or am I wrong?). The raid 0 would be backed up to another drive regularly.

I havent messed with raid for years, not since scsi.

[alsenior]

don't suppose by chance that is a ibm serveraid controller is it?

with raid 5 there is only a performance drop on write or if there is a crc error form the drive on read in witch case it recreates the data from parity

[Magnets]

I would presume that if you were using write back cache, disk cache size would make a significant difference.

[DataMatrix]

How many HDDs do you plan on using? What controller?

I would say if you are planning on redundancy, using the write back cache isn't a good idea... If the system loses power while writing, the RAID 5 array is useless...

If you have enough HDDs for RAID 5 the performance drop is insignificant. My RAID array is a nice balance of performance and redundancy.

[Clunk]

don't suppose by chance that is a ibm serveraid controller is it?

with raid 5 there is only a performance drop on write or if there is a crc error form the drive on read in witch case it recreates the data from parity

Thanks, no its an Adaptec, and I think its a 3805, although he hasnt arrived with it yet.

How many HDDs do you plan on using? What controller?

Dunno yet, thats why I'm asking about the cache on the hard drives.

I almost bought 4x WD drives last night that are on offer at ebuyer, and at the last minute I looked at the reviews and all the recent ones are one star

Will see whats cheap.

[alsenior]

http://www.scan.co.uk/Products/Produ...oductID=397203

these would be cracking drives

edit: ohh reassuringly good card

[Clunk]

Thanks for that, wasnt sure if it was decent or not, couldnt find much info. Luckily, it came with the right cables, which are quite weird looking things.

Seagate and Maxtor are out of the question for me unfortunately, too many dead ones, admittedly most are maxtor, but dont want to take any chances there.

I was looking at these, I have a 400gb version, and that has been excellent, whaddaya reckon? Bit cheaper as well.

[alsenior]

they would do you good.

i believe the controller end of the cable is an infiniband connector.

also they support staggered spin up which can be a hand in large raid sets and is something that up to now i had only seen on scsi drives.

also as a side note that controller suppors sas should you want something recklessly fast.

[Clunk]

I've gone for the Samsungs, decent spec, decent price, and pretty quiet.

Heres a pic of the connector on the end of the cable, its about the same width as a standard sata cable at the tip (give or take a few mm).




Drives wont arrive til friday, so will report back then

[Zak33]

you know what...I have never ever thought about the impace of the cache on a hard drive for a RAID system.

So I shall not join in this discussion

[Clunk]

Hmmm, a cryptic message...but what does it mean?

[alsenior]

spam from zak get him out of here