My apology for cross posting We have a DELL6850 with 8Gbytes of memory, four 3.2Ghz CPU's , perc 4 raid controller, with fourteen 300Gbyte 10Krpm disk on a powervault 220s, And a powervault 124T LTO-3 tape systems on a separate 160Mbyte/sec adaptec SCSI card. The disks are configured as two 2Tbyte raid 0 partitions using the perc 4 hardware. The problem is - reading from the disk, and writing to the tape is pathetically slow. The specs say I should get around 80Mbyte/second - in reality - is about 500 Kbytes/second Writing just to tape, using /dev/zero as input and dd to write, I can get up to 60Mybte/second, indicating that the tape drive and scsi card is functional from a hardware perspective. Since I can read and write data to the disks - I assume that they are functional. The files are 80Mybtes for the minimum size that I am writing to tape. DELL Support hides behind the fact that CENTOS is not a supported OS, But RED HAT is - so switch to it, so DELL can get RED HAT Support involved. And the fact that Rocks is a modification to an unsupported OS.... I have tried using various block size in tar from 256 to 8192 - with minimal success. Does anybody have any experience on setting the OS/Kernel parameters to utilize the hardware at something more then a snails pace? Or Suggestions on what I could test and/or try? Or Is there a standard disk / tape IO test package that could test the speed/performance of the disks and /or tapes? Thanks for your help Dan A. Dansereau
And what about a raw disk tape to raw tape copy ? # dd if=/dev/sda of=/dev/nst0 bs=32k count=32768 PS: 14 disk in raid 0 is very fragile, this should be used only for caching data. With a PV220 maybe a backup engine then ! On 9/2/07, Dan Dansereau <ddansereau at hydropoint.com> wrote:> My apology for cross posting > > We have a DELL6850 with 8Gbytes of memory, four 3.2Ghz CPU's , perc 4 > raid controller, with fourteen 300Gbyte 10Krpm disk on a powervault > 220s, And a powervault 124T LTO-3 tape systems on a separate > 160Mbyte/sec adaptec SCSI card. > The disks are configured as two 2Tbyte raid 0 partitions using the perc > 4 hardware. > > The problem is - reading from the disk, and writing to the tape is > pathetically slow. > The specs say I should get around 80Mbyte/second - in reality - is about > 500 Kbytes/second > > Writing just to tape, using /dev/zero as input and dd to write, I can > get up to 60Mybte/second, indicating that the tape drive and scsi card > is functional from a hardware perspective. Since I can read and write > data to the disks - I assume that they are functional. > The files are 80Mybtes for the minimum size that I am writing to tape. > > DELL Support hides behind the fact that CENTOS is not a supported OS, > But RED HAT is - so switch to it, so DELL can get RED HAT Support > involved. And the fact that Rocks is a modification to an unsupported > OS.... > > I have tried using various block size in tar from 256 to 8192 - with > minimal success. > > Does anybody have any experience on setting the OS/Kernel parameters to > utilize the hardware at something more then a snails pace? > Or > Suggestions on what I could test and/or try? > Or > Is there a standard disk / tape IO test package that could test the > speed/performance of the disks and /or tapes? > > Thanks for your help > Dan A. Dansereau > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos >-- Alain Spineux aspineux gmail com May the sources be with you
Dan Dansereau wrote:> My apology for cross posting > > We have a DELL6850 with 8Gbytes of memory, four 3.2Ghz CPU's , perc 4 > raid controller, with fourteen 300Gbyte 10Krpm disk on a powervault > 220s, And a powervault 124T LTO-3 tape systems on a separate > 160Mbyte/sec adaptec SCSI card. > The disks are configured as two 2Tbyte raid 0 partitions using the perc > 4 hardware. > > The problem is - reading from the disk, and writing to the tape is > pathetically slow. > The specs say I should get around 80Mbyte/second - in reality - is about > 500 Kbytes/second > > Writing just to tape, using /dev/zero as input and dd to write, I can > get up to 60Mybte/second, indicating that the tape drive and scsi card > is functional from a hardware perspective. Since I can read and write > data to the disks - I assume that they are functional. > The files are 80Mybtes for the minimum size that I am writing to tape. > > DELL Support hides behind the fact that CENTOS is not a supported OS, > But RED HAT is - so switch to it, so DELL can get RED HAT Support > involved. And the fact that Rocks is a modification to an unsupported > OS.... > > I have tried using various block size in tar from 256 to 8192 - with > minimal success. > > Does anybody have any experience on setting the OS/Kernel parameters to > utilize the hardware at something more then a snails pace? > Or > Suggestions on what I could test and/or try?I don't know anything about this specific hardware, but the usual problem with tape is that if you can't feed it fast enough to stream at its native speed it has to constantly stop, back up, and restart to write the next chunk. Single-threaded programs normally can't because they wait for a read to complete before starting the write. There are programs around like mbuffer that allow the reading and writing to overlap and provide a large buffer to minimize the restarts even if the average throughput is still too slow. Tapes also have a 'block size' that you can set with mt, and some particular size may provide the best speed. With some drives, the write block size from tar or obs= in dd must exactly match the tape block size or be exact multiples. -- Les Mikesell lesmikesell at gmail.com
> Does anybody have any experience on setting the OS/Kernel parameters to > utilize the hardware at something more then a snails pace?My guess is, that the CentOS kernel doesn't contain a driver for your harddisk controller, and thus is falling back to some generic driver. Refer to the controller's manufacturer and find out / ask how to use it with Linux. Patrick. -- Key ID: 0x86E346D4 http://patrick-nagel.net/key.asc Fingerprint: 7745 E1BE FA8B FBAD 76AB 2BFC C981 E686 86E3 46D4 -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 189 bytes Desc: This is a digitally signed message part. URL: <http://lists.centos.org/pipermail/centos/attachments/20070903/880bee42/attachment.sig>
On Sun, 2 Sep 2007 at 8:11am, Dan Dansereau wrote> We have a DELL6850 with 8Gbytes of memory, four 3.2Ghz CPU's , perc 4 > raid controller, with fourteen 300Gbyte 10Krpm disk on a powervault > 220s, And a powervault 124T LTO-3 tape systems on a separate > 160Mbyte/sec adaptec SCSI card.Which card and driver? ISTR folks having issues with adaptec cards and LTO3 drives. Might you have a spare LSI SCSI card (ultra320, preferably) about that you could test with?> The disks are configured as two 2Tbyte raid 0 partitions using the perc > 4 hardware. > > The problem is - reading from the disk, and writing to the tape is > pathetically slow. > The specs say I should get around 80Mbyte/second - in reality - is about > 500 Kbytes/secondHave you benchmarked the disks to make sure you get decent performance out of them?> Writing just to tape, using /dev/zero as input and dd to write, I can > get up to 60Mybte/second, indicating that the tape drive and scsi card > is functional from a hardware perspective. Since I can read and write > data to the disks - I assume that they are functional. > The files are 80Mybtes for the minimum size that I am writing to tape.80MB total or lots of 80MB files? If the former, you really need to test with, IMO, at least 2X RAM (preferably 4X) sized data to get a reliable speed estimate.> Is there a standard disk / tape IO test package that could test the > speed/performance of the disks and /or tapes?bonnie++ is somewhat standard for testing disk sequential read/write speeds. -- Joshua Baker-LePain Department of Biomedical Engineering Duke University