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From: Tony Harding on 29 May 2010 19:59 Many posters here and elsewhere have recommended implementing RAID via hardware rather than software, so I Googled "pc raid controller card" and got a zillion hits with prices ranging from $20 to $800. Asking for advice concerning what I actually need on such a card, e.g., ports, memory, etc. IIRC Adaptec has (or had) a good reputation for their SCSI cards, are they still a good brand? How about Silicon Image (I have one of their SATA cards)? TIA, Tony H
From: William R. Walsh on 1 Jun 2010 11:43 Hi! > Many posters here and elsewhere have recommended implementing > RAID via hardware rather than software, so I Googled "pc raid > controller card" and got a zillion hits with prices ranging from $20 > to $800. That's because the term "RAID" is abused to include fakeraid cards, of which there are a lot. Silicon Image, VIA, Marvell and Initio SATA controllers all implement some degree of fake RAID in their firmware. Adaptec and 3Ware both sell real hardware RAID cards, as do some other companies. Here's an Adaptec 3405 card, which is a real hardware RAID controller for four SATA/SAS hard disks: http://www.adaptec.com/en-US/products/Controllers/Hardware/sas/value/SAS-3405/ > Asking for advice concerning what I actually need on such a > card, e.g., ports, memory, etc. Any real hardware RAID card has a processor of some type on it to do the XOR calculations needed by RAID-5, and to perform various other housekeeping tasks. Any RAM the adapter has is usually used by its processor. Usually the amount of installed RAM is fixed. Some RAID cards do have expandable RAM, but it's unlikely that you will need such a capability. Others have optional add-on write cache units, usually with battery backups (in case the power fails while a disk write is being held in the cache). You probably don't need that either. There will also be an alarm buzzer of some kind to indicate that a disk failure has occurred. This is a very loud and annoying device. (Trust me on this. ;-)) Real hardware RAID cards typically use a SATA controller from Silicon Image, Marvell or someone else. But that IC is used only as a disk controller--RAID functions are handled using other logic on the adapter. That is what sets a real hardware RAID card apart from a "fakeraid" card...it has the ability to function on its own and do everything it needs to do all by itself. As to how many disks you need, that depends upon what you plan to do: RAID 1 and RAID 0 both need at least two disks. RAID5 requires at least three (two data, one parity) and preferably four (two data, one parity, and one hot spare that is kept idle) disks. > IIRC Adaptec has (or had) a good reputation for their SCSI > cards, are they still a good brand? Adaptec makes excellent products for the most part, but they have started to dabble in "fake RAID" cards, with something that they call "Host RAID". This would be best avoided from what I have heard. > How about Silicon Image (I have one of their SATA cards)? That is most probably a plain serial ATA controller with fake RAID support tossed in for an added bonus. Silicon Image actually provides two add-in BIOSes for their cards. One is the so-called "IDE" BIOS that makes the card into a simple serial ATA storage controller. The other is the fake RAID BIOS. As the fake RAID is typically nothing but trouble in the applications where I use the cards (FreeNAS, etc) and I'm not using RAID anyway, I flash the plain BIOS to the cards so there's no special "magic" getting in the way. William
From: Tony Harding on 1 Jun 2010 12:35 On 06/01/10 11:43, William R. Walsh wrote: > Hi! > >> Many posters here and elsewhere have recommended implementing >> RAID via hardware rather than software, so I Googled "pc raid >> controller card" and got a zillion hits with prices ranging from $20 >> to $800. > > That's because the term "RAID" is abused to include fakeraid cards, of > which there are a lot. Silicon Image, VIA, Marvell and Initio SATA > controllers all implement some degree of fake RAID in their firmware. > > Adaptec and 3Ware both sell real hardware RAID cards, as do some other > companies. Here's an Adaptec 3405 card, which is a real hardware RAID > controller for four SATA/SAS hard disks: > > http://www.adaptec.com/en-US/products/Controllers/Hardware/sas/value/SAS-3405/ > >> Asking for advice concerning what I actually need on such a >> card, e.g., ports, memory, etc. > > Any real hardware RAID card has a processor of some type on it to do > the XOR calculations needed by RAID-5, and to perform various other > housekeeping tasks. > > Any RAM the adapter has is usually used by its processor. Usually the > amount of installed RAM is fixed. Some RAID cards do have expandable > RAM, but it's unlikely that you will need such a capability. Others > have optional add-on write cache units, usually with battery backups > (in case the power fails while a disk write is being held in the > cache). You probably don't need that either. > > There will also be an alarm buzzer of some kind to indicate that a > disk failure has occurred. This is a very loud and annoying device. > (Trust me on this. ;-)) > > Real hardware RAID cards typically use a SATA controller from Silicon > Image, Marvell or someone else. But that IC is used only as a disk > controller--RAID functions are handled using other logic on the > adapter. That is what sets a real hardware RAID card apart from a > "fakeraid" card...it has the ability to function on its own and do > everything it needs to do all by itself. > > As to how many disks you need, that depends upon what you plan to do: > RAID 1 and RAID 0 both need at least two disks. > > RAID5 requires at least three (two data, one parity) and preferably > four (two data, one parity, and one hot spare that is kept idle) > disks. > >> IIRC Adaptec has (or had) a good reputation for their SCSI >> cards, are they still a good brand? > > Adaptec makes excellent products for the most part, but they have > started to dabble in "fake RAID" cards, with something that they call > "Host RAID". This would be best avoided from what I have heard. > >> How about Silicon Image (I have one of their SATA cards)? > > That is most probably a plain serial ATA controller with fake RAID > support tossed in for an added bonus. > > Silicon Image actually provides two add-in BIOSes for their cards. One > is the so-called "IDE" BIOS that makes the card into a simple serial > ATA storage controller. The other is the fake RAID BIOS. > > As the fake RAID is typically nothing but trouble in the applications > where I use the cards (FreeNAS, etc) and I'm not using RAID anyway, I > flash the plain BIOS to the cards so there's no special "magic" > getting in the way. Thanks, William, for such an informative (& lengthy) reply. I feel now as though I could shop for & buy a RAID Controller Card and get it right. :) Minor nit, my Silicon Image SATA card is SATA HDDs only, no hint of RAID to it at all. Reason I asked about SI is because I've used 2 of their SiI 3132 cards for a few years now and they've been rock solid. That's apparently what they're good at, not RAID.
From: William R. Walsh on 1 Jun 2010 12:53
Hi! > Thanks, William, for such an informative (& lengthy) reply. I want to be sure that I've covered everything. Plus, I like typing. (Having a good keyboard--IBM Model M--tends to do that!) > Minor nit, my Silicon Image SATA card is SATA HDDs only, no > hint of RAID to it at all. That's what I was saying with the last bit. Silicon Image provides two different BIOS types for their adapters...one that does "RAID" and one that does not. You probably have the one that doesn't--or you've never configured an "array". I've been very happy with the Silicon Image chipsets (3112, 3114, 3512) for the most part. When they're just acting as SATA controllers, they do a very good job. I only found one application where they didn't work, and that was in an HP Vectra Pentium Pro tower that I turned into a FreeNAS box. He who admits to putting a SATA controller card into such a machine probably deserves exactly what he gets. ;-) If you thought I wrote a lot before, you might not want to read this: http://greyghost.mooo.com/timecapsule-vs-freenas/ The shortened version of that story is that a ~14 year old PC does a better and faster job than does an Apple Time Capsule...and the price sure is right! William |