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NOTICE: This version of the NSF Unidata web site (archive.unidata.ucar.edu) is no longer being updated.
Current content can be found at unidata.ucar.edu.
To learn about what's going on, see About the Archive Site.
RAID 6 is the way we're going simply because we want to survive the 2-disk failures we've seen in the past (twice I can think of).
gerry Rob Cermak wrote:
RAID 1? I like Gerry's idea of moving from RAID 5 to 6. A recent hardware raid driver that moved into recent kernels is the Areca driver. We have this card sitting in a 16 SATA drive array and we have it currently broken up into 4 raid volumes.We had a 750GB disk die. The volume affected went in to degraded mode. We swapped the disk out and the volume regenerated automatically. Took4.5 hours, but it regenerated. During this 4.5 hour rebuild, two things can happen: (1) you can lose another disk and your whole volume is toast, (2) find out the new disk you swapped in is bad. Anyway, this whole proceedure did not require any downtime. The OS (Mandriva 2007) didn't notice a thing. Granted I/O was a bit slower during the degraded period and rebuild. http://www.areca.com.tw/ The raid card requires a PCI-X slot. But it is a hardware raid and I think servicable from the Linux side, but we use the NIC port on the card to talk to the built in webserver. The NIC card can also be configured to send SNMP messages or email when states change on the raid. The raid card also emits a loud beep (much like a UPS overload) that you can acknowledge and turn off. That takes care of problems where email notification fails. Another group referred us to this card and to a company that sells the card in the enclosures, if you want that referral, I will email it to you off-list. Or, you can roll your own as the card itself can be found. Rob # dmesg | grep -i areca ARECA RAID ADAPTER0: FIRMWARE VERSION V1.39 2006-2-9 scsi0 : Areca SATA Host Adapter RAID Controller( RAID6 capable) At RAID 5, 4 x 500 GB SATA volume will net you about 1.4Tb of space. Filesystem Size Used Avail Use% Mounted on /dev/sdd1 1.4T 472G 834G 37% /arsc # lspci | grep -i areca 02:0e.0 RAID bus controller: Areca Technology Corp. ARC-1160 16-Port PCI-X to SATA RAID Controller # uname -a Linux some.host.edu 2.6.22.1 #1 SMP Thu Jul 12 16:44:37 AKDT 2007 i686 Dual Core AMD Opteron(tm) Processor 285 GNU/Linux On Mon, October 15, 2007 9:44 pm, Gilbert Sebenste wrote:On Mon, 15 Oct 2007, Michael Dross wrote:Hope this is not too far off topic... SAS is SCSI. "Serial Attached SCSI" It's just a "newer/better" version so to speak. SAS drives are to SATA, like SCSI is/was to IDE... in terms of performance... if that makes any sense. Overly simplified, but hopefully draws a connection. Now the confusing part is that a SAS designed backplane and controller will work with SATA II drives. But most folks that have paid the premium for SAS raid controllers, need the performance and usually install SAS drives, despite their higher cost.Cool. Well, here's where I ask another question. Starting in February, as UNIDATA points out oh so well, for those of us who love the Level 2 radar data...we're going to love it a lot more. To the tune of 2.3 times more, in terms of file size. Only the lower tilts will have the "super resolution", but let's face it: those file sizes aren't going to be small. So I am thinking this. I am on a pretty tight budget, and yet I want the Level 2 data...from every site... I buy a RAID 1 array. This means I have two 750 GB SATA drives, running SATA 1 until either the Kernel or the OS or the hardware firmware gets straightened out. I have 1.5 GB/sec throughput on each drive. If one hard drive blows up, everything is still cool and things keep chugging along. And, I (hope) things can be rebuilt on the blown second drive automagically. So my questions are: 1. Is this going to be fast enough to handle Level 2 data starting next spring? 2. How do you set this up? 3. What specific hardware is needed? (Yes, I've never done this before.) 4. Or do I tell my boss that I REALLY need SCSI or SAS drives to do a RAID 1 array with what I am going to do? ******************************************************************************* Gilbert Sebenste ******** (My opinions only!) ****** Staff Meteorologist, Northern Illinois University **** E-mail: sebenste@xxxxxxxxxxxxxxxxxxxxx *** web: http://weather.admin.niu.edu ** ******************************************************************************* _______________________________________________ ldm-users mailing list ldm-users@xxxxxxxxxxxxxxxx For list information or to unsubscribe, visit: http://www.unidata.ucar.edu/mailing_lists/
-- Gerry Creager -- gerry.creager@xxxxxxxx Texas Mesonet -- AATLT, Texas A&M University Cell: 979.229.5301 Office: 979.862.3982 FAX: 979.862.3983 Office: 1700 Research Parkway Ste 160, TAMU, College Station, TX 77843
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