RE: Hardware RAID Advice Sought
Hi Doug, I have been digging around in archives, etc, but can't decide which hardware raid controller will be the best for Linux. The options for U160 multichannel hardware RAID seem to be the Mylex ExtremeRAID 2000, the Adaptec 3400S, and the AMI MegaRAID (Elite/Enterprise 1600). I'm using the AMI MegaRAID (Elite1600) and the Mylex ExtremeRAID (ExtremeRAID1100 - the 2000 is quite new so not sure about this one). These both have mature drivers. Can't say I know about the Adaptec 3400S - can't seem to find much info/experience about running it with Linux - maybe uses I2O which isn't as mature on Linux?? The AMI I think has a few more benefits IMHO than the Mylex: * It supports non-disk devices (ie. tape units, SAF-TE processors etc) (The Mylex supports SAF-TE but doesn't allow access to it from Linux AFAIK - From Linux's point of view, the Mylex is not a scsi driver, its a special disk block driver - with no generic SCSI interface) * AMI supports 64bit/66MHz - the others are 64bit/33MHz * It has a Linux gui (megamanager) for configuring logical disks (the mylex requires you to reboot into BIOS AFAIK) * It is a scsi device rather than a proprietary block device (like the Mylex DAC960) meaning you can take advantage of more generic scsi infrastructure such as 'echo 'scsi add-single-device 1 0 1 0 /proc/scsi/scsi' for dynamically adding disk devices (although DAC960 driver does have some pretty neat /proc/ filesystem stuff for monitoring/starting rebuilds etc) I'm using both of these for shared-scsi clustering - both of them support multi-initiator clustering so you can have two hosts talking to the same disks. I'm still testing the AMI but my Mylex in production has been running seamlessly on a shared-SCSI bus for over 6months. Both the AMI and Mylexs required firmware upgrades to get it to work with my disks but after this - it seems to be working like a dream (out of the box RH6.2 detects AMI or DAC and works fine - i'm now using megaraid driver in 2.4.3 and has been okay with my testing so far). Funny thing is though - I get better performance using Software-RAID on 2.2 kernels using a non RAID adaptec 7899 than with either of these RAID controllers. Unfortunately I can't use Software RAID in a clustered environment and hardware RAID makes me feel a lot more comfortable. I won't have time for constant tinkering, so mature hassle-free drivers and support software is probably my number one concern any hints for me? The motherboard supports 64bit/66MHz PCI, btw. And, from the what-a-newbie column, maybe someone can help me out here: If I buy 3 HDs now, and put them together in a RAID5, can I simply add 3 more drives later on? I don't neccesarily want to resize the existing partitions, but rather to be able to add new ones within the RAID. It seems like this would be a common thing, but I seem to recall an email saying this is problematic. No worries, just add another logical disk using the 3 new drives - will appear as another SCSI device. It should be possible to do this without a reboot with the AMI (although haven't tried this yet) if you have a hot-swapable drive cabinet. ~mc - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED]
RE: Hardware RAID Advice Sought
On Thu, 26 Apr 2001, Holger Kiehl wrote: Thanks for all the help. Basic real-world questions like this don't tend to make it into faqs, but can go a long way to helping you make informed buying decisions. Why not try software raid? Its faster and cheaper. I would rather spend the money than incur the CPU overhead from software RAID. The benchmarks I have seen put 3-6 disk software RAID at a 15-30% CPU utilization. The machine will be constantly running CPU-intensive code, so that is too painful a hit to take. Thanks, D - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED]
Re: Hardware RAID Advice Sought
On Thu, Apr 26, 2001 at 06:26:44PM +0200, Holger Kiehl wrote: On Thu, 26 Apr 2001, root wrote: OK, a stupid follow-up question: if I start with 3 drives in a RAID5, I will have 2 data drives and 1 parity drive, correct? Now, if I add 3 more drives as a second logical volume, will I have to devote 1 of them to parity again, or can the initial parity drive be used for both? I would like reserve as many of the drives for data as possible, even if it means spending more money in the near term to get all 6 drives. In raid 4 you have a parity disk, in raid 5 the parity is stripped across all disks. true. anyway for disk waste it is the same you always have N-1 in a raid5 if you add a second logical volume (=raid array) it is a different array so it needs a different parity. you can anyway extend the current raid5 (at least with AMI -i tried hp netraids 1 3). Thanks for all the help. Basic real-world questions like this don't tend to make it into faqs, but can go a long way to helping you make informed buying decisions. Why not try software raid? Its faster and cheaper. yup, but with hw raid you save cpu cycles and, more important you have a battery backup. L. -- Luca Berra -- [EMAIL PROTECTED] Communication Media Services S.r.l. /\ \ / ASCII RIBBON CAMPAIGN XAGAINST HTML MAIL / \ - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED]
RE: Hardware RAID Advice Sought
On Thu, 26 Apr 2001, Michael Clark wrote: The AMI I think has a few more benefits IMHO than the Mylex: How about performance? I've read that the Mylex is more of a hardware solution since it uses ASICs to do lots of the computation work, whereas the AMI is essentially running software on its i960. Don't know if this is true or not. Of course, the AMI is about 1/2 the price... No worries, just add another logical disk using the 3 new drives - will appear as another SCSI device. It should be possible to do this without a reboot with the AMI (although haven't tried this yet) if you have a hot-swapable drive cabinet. OK, a stupid follow-up question: if I start with 3 drives in a RAID5, I will have 2 data drives and 1 parity drive, correct? Now, if I add 3 more drives as a second logical volume, will I have to devote 1 of them to parity again, or can the initial parity drive be used for both? I would like reserve as many of the drives for data as possible, even if it means spending more money in the near term to get all 6 drives. Thanks for all the help. Basic real-world questions like this don't tend to make it into faqs, but can go a long way to helping you make informed buying decisions. -D - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED]
RE: Hardware RAID Advice Sought
Why not try software raid? Its faster and cheaper. I would rather spend the money than incur the CPU overhead from software RAID. And though it was not a consideration in the beginning, SW Raid doesn't really support hot-plug, does it? -- / C. R. (Charles) Oldham | NCA-CASI \ / Director of Technology | Arizona State University \ / [EMAIL PROTECTED] | V:480-965-8703 F:480-965-9423 \ - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED]
Re: Hardware RAID Advice Sought
Howdy! C. R. Oldham wrote: Why not try software raid? Its faster and cheaper. I would rather spend the money than incur the CPU overhead from software RAID. And though it was not a consideration in the beginning, SW Raid doesn't really support hot-plug, does it? Sure it does, if you buy a drive enclosure which handles it. We're very happy with our Kingston enclosure; turn a key and down goes the power, swap, and trun the key again. =] Cheers! --j -- Jim Meyer, Geek At Large [EMAIL PROTECTED] - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED]
Re: Hardware RAID Advice Sought
From [EMAIL PROTECTED] Thu Apr 26 12:22:57 2001 Howdy! C. R. Oldham wrote: Why not try software raid? Its faster and cheaper. I would rather spend the money than incur the CPU overhead from software RAID. And though it was not a consideration in the beginning, SW Raid doesn't really support hot-plug, does it? Sure it does, if you buy a drive enclosure which handles it. We're very happy with our Kingston enclosure; turn a key and down goes the power, swap, and trun the key again. =] And it doesn't hang the scsi bus? What controller are you using? Which model enclosure are you using? Cheers, Chris -- Chris Mauritz [EMAIL PROTECTED] - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED]
Re: Hardware RAID Advice Sought
Howdy!
ritz wrote:
From [EMAIL PROTECTED] Thu Apr 26 12:22:57 2001
C. R. Oldham wrote:
Why not try software raid? Its faster and cheaper.
I would rather spend the money than incur the CPU overhead
from software RAID.
Hmmm. The money you'll spend on that might buy you a faster processor,
if that's possible. You also may want to investigate multi-proc configs,
though that only became possible in kernel 2.4.2-ish if I remember
correctly.
And though it was not a consideration in the beginning, SW Raid doesn't
really support hot-plug, does it?
Sure it does, if you buy a drive enclosure which handles it. We're very
happy with our Kingston enclosure; turn a key and down goes the power,
swap, and trun the key again. =]
And it doesn't hang the scsi bus?
Nope. You have to go about this in an organized fashion; here's our docs
on how to remove a failed drive -- we'll use /dev/sdd (SCSI ID 3) as an
example:
raidhotremove /dev/md0 /dev/sdd1
echo 'scsi remove-single-device 0 0 3 0' /proc/scsi/scsi
...power off the drive, pull it, put in the new prepared (e.g. fdisk'd
and partitioned as one big partition of type fd) drive, power on the
drive...
echo 'scsi add-single-device 0 0 3 0' /proc/scsi/scsi
raidhotadd /dev/md0 /dev/sdd1
Incidentally, the four values in the echo are Host, Channel, SCSI ID,
and LUN.
What controller are you using?
Here's /proc/scsi/aic7xxx/0:
Adaptec AIC7xxx driver version: 5.1.28/3.2.4
Compile Options:
TCQ Enabled By Default : Enabled
AIC7XXX_PROC_STATS : Enabled
AIC7XXX_RESET_DELAY: 5
Adapter Configuration:
SCSI Adapter: Adaptec AIC-7892 Ultra 160/m SCSI host adapter
Ultra-160/m LVD/SE Wide Controller at PCI
0/16/0
PCI MMAPed I/O Base: 0xffaff000
Adapter SEEPROM Config: SEEPROM found and used.
Adaptec SCSI BIOS: Enabled
IRQ: 11
SCBs: Active 0, Max Active 64,
Allocated 75, HW 32, Page 255
Interrupts: 103457029
BIOS Control Word: 0xb8f4
Adapter Control Word: 0x7c5d
Extended Translation: Enabled
Disconnect Enable Flags: 0x
Ultra Enable Flags: 0x
Tag Queue Enable Flags: 0x01ff
Ordered Queue Tag Flags: 0x01ff
Default Tag Queue Depth: 8
Tagged Queue By Device array for aic7xxx host instance 0:
{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}
Actual queue depth per device for aic7xxx host instance 0:
{8,8,8,8,8,8,8,8,8,1,1,1,1,1,1,1}
Which model enclosure are you using?
An excellent question, and one I think I'll need to ask someone here
before I can answer further than Kingston and probably an InfoStation
or of that sort.
Cheers!
--j
--
Jim Meyer, Geek At Large [EMAIL PROTECTED]
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Hardware RAID Advice Sought
Hello, I am building a brand new server box and would like some input by the experts on what hardware to buy. The box will be a Supermicro 370DE6, with dual PIII-1GHz, running Linux kernel 2.4.x I was thinking of going with the new Seagate Barracuda 180s in a RAID 5 setup. 5 drives (+ 1 parity drive) gets you 900GB of disk space for about $10k. They are thick bastards, but I don't need hot-swap, etc. How much benefit would there be getting the 16MB cache version versus the 4MB cache? I have been digging around in archives, etc, but can't decide which hardware raid controller will be the best for Linux. The options for U160 multichannel hardware RAID seem to be the Mylex ExtremeRAID 2000, the Adaptec 3400S, and the AMI MegaRAID (Elite/Enterprise 1600). I won't have time for constant tinkering, so mature hassle-free drivers and support software is probably my number one concern any hints for me? The motherboard supports 64bit/66MHz PCI, btw. And, from the what-a-newbie column, maybe someone can help me out here: If I buy 3 HDs now, and put them together in a RAID5, can I simply add 3 more drives later on? I don't neccesarily want to resize the existing partitions, but rather to be able to add new ones within the RAID. It seems like this would be a common thing, but I seem to recall an email saying this is problematic. OK, thanks for your time, Doug (shamelessly posting as root) - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED]
Re: Hardware RAID Advice Sought
I can comment on the part about the cache size. The decision to go with higher or lower cache sizes usually has to do with what size files are being stored and read. I have spoken to seagate about this and their comment is that the larger harddisk cache sizes are more useful for very large files and applications such as digital imaging and filesystem imaging. For database / multiple database applications the cache size becomes less important and seek speeds and system ram becomes more important. In either case, if money is not an issue, more is better. I hope this helps. Charles Wilkins - Original Message - From: root [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Wednesday, April 25, 2001 3:30 PM Subject: Hardware RAID Advice Sought Hello, I am building a brand new server box and would like some input by the experts on what hardware to buy. The box will be a Supermicro 370DE6, with dual PIII-1GHz, running Linux kernel 2.4.x I was thinking of going with the new Seagate Barracuda 180s in a RAID 5 setup. 5 drives (+ 1 parity drive) gets you 900GB of disk space for about $10k. They are thick bastards, but I don't need hot-swap, etc. How much benefit would there be getting the 16MB cache version versus the 4MB cache? I have been digging around in archives, etc, but can't decide which hardware raid controller will be the best for Linux. The options for U160 multichannel hardware RAID seem to be the Mylex ExtremeRAID 2000, the Adaptec 3400S, and the AMI MegaRAID (Elite/Enterprise 1600). I won't have time for constant tinkering, so mature hassle-free drivers and support software is probably my number one concern any hints for me? The motherboard supports 64bit/66MHz PCI, btw. And, from the what-a-newbie column, maybe someone can help me out here: If I buy 3 HDs now, and put them together in a RAID5, can I simply add 3 more drives later on? I don't neccesarily want to resize the existing partitions, but rather to be able to add new ones within the RAID. It seems like this would be a common thing, but I seem to recall an email saying this is problematic. OK, thanks for your time, Doug (shamelessly posting as root) - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED]
Re: Hardware RAID Advice Sought
not sure which is better... megaraid, extremraid or adaptec... I can suggest the Mylex extremeRAID cards. We haven't run into a problem so far and the driver http://www.dandelion.com/Linux/DAC960.html is part of the kernel for a very long time, ie. it has a proven stability and you can install a distribution directly onto a RAID disk. - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED]
