I have a perc5i (and perc5e) raid controller in my poweredge 2970 running centos 5.5. The RAID controller config is set for write-back policy, which I can confirm by checking in OpenManage. I also called Dell and ran their reporting application and had them double check to make sure everything looks OK hardware wise and they confirm that it does
Yet when CentOS boots is appears to use the write through policy as can be seen below from dmesg output. Am I wrong that CentOS should query the RAID controller and go into the correct write mode: write-back?
hub 1-5:1.0: 4 ports detected Vendor: DP Model: BACKPLANE Rev: 1.00 Type: Enclosure ANSI SCSI revision: 05 Vendor: DELL Model: PERC 5/i Rev: 1.03 Type: Direct-Access ANSI SCSI revision: 05 SCSI device sda: 2435317760 512-byte hdwr sectors (1246883 MB) sda: Write Protect is off sda: Mode Sense: 1f 00 00 08 SCSI device sda: drive cache: write through SCSI device sda: 2435317760 512-byte hdwr sectors (1246883 MB) sda: Write Protect is off sda: Mode Sense: 1f 00 00 08 SCSI device sda: drive cache: write through sda: sda1 sda2 sda3 sd 0:2:0:0: Attached scsi disk sda megasas: 0x1028:0x0015:0x1028:0x1f01: bus 16:slot 14:func 0 GSI 21 sharing vector 0x62 and IRQ 21 ACPI: PCI Interrupt 0000:10:0e.0[A] -> GSI 18 (level, low) -> IRQ 98 megasas: FW now in Ready state
Can anyone with write-back cache working just confirm that they see some sort of indication of write-back in dmesg?
As I mentioned I talked with Dell and they claim it is working, however I spoke with VMWare and they said if it isn't indicated in dmesg, then it isn't working. It would just be good to know it is indicated as functional in this way for others so I can have something to go on with Dell.
On 2/11/2011 10:00 AM, James Chase wrote:
I have a perc5i (and perc5e) raid controller in my poweredge 2970 running centos 5.5. The RAID controller config is set for write-back policy, which I can confirm by checking in OpenManage. I also called Dell and ran their reporting application and had them double check to make sure everything looks OK hardware wise and they confirm that it does
Yet when CentOS boots is appears to use the write through policy as can be seen below from dmesg output. Am I wrong that CentOS should query the RAID controller and go into the correct write mode: write-back?
hub 1-5:1.0: 4 ports detected Vendor: DP Model: BACKPLANE Rev: 1.00 Type: Enclosure ANSI SCSI revision: 05 Vendor: DELL Model: PERC 5/i Rev: 1.03 Type: Direct-Access ANSI SCSI revision: 05 SCSI device sda: 2435317760 512-byte hdwr sectors (1246883 MB) sda: Write Protect is off sda: Mode Sense: 1f 00 00 08 SCSI device sda: drive cache: write through SCSI device sda: 2435317760 512-byte hdwr sectors (1246883 MB) sda: Write Protect is off sda: Mode Sense: 1f 00 00 08 SCSI device sda: drive cache: write through sda: sda1 sda2 sda3 sd 0:2:0:0: Attached scsi disk sda megasas: 0x1028:0x0015:0x1028:0x1f01: bus 16:slot 14:func 0 GSI 21 sharing vector 0x62 and IRQ 21 ACPI: PCI Interrupt 0000:10:0e.0[A] -> GSI 18 (level, low) -> IRQ 98 megasas: FW now in Ready state
CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
on 2/16/2011 5:31 AM James Chase spake the following:
Can anyone with write-back cache working just confirm that they see some sort of indication of write-back in dmesg?
SCSI device sda: drive cache: write back, no read (daft) SCSI device sda: drive cache: write back, no read (daft) SCSI device sdb: drive cache: write through SCSI device sdb: drive cache: write through
But not a PERC... Maybe your driver is not reporting back properly?
On Wed, Feb 16, 2011 at 08:31:05AM -0500, James Chase wrote:
Can anyone with write-back cache working just confirm that they see some sort of indication of write-back in dmesg?
As I mentioned I talked with Dell and they claim it is working, however I spoke with VMWare and they said if it isn't indicated in dmesg, then it isn't working. It would just be good to know it is indicated as functional in this way for others so I can have something to go on with Dell.
You can verify your cache policy with MegaCLI tool. Check your output from `MegaCli -CfgDsply -a0' command.
You can verify your cache policy with MegaCLI tool. Check your output from `MegaCli -CfgDsply -a0' command.
What a cool tool. It looks like it should be active according to MegaCli, though strange that Scott sees his drives in write-back mode via CentOS and I do not and I also have these horrific NFS speeds via VMWare that so many people have found to be caused by write-back not being active...
I don't know what the answer is to this question. I went with iSCSI instead of NFS, the benefits being that it trounces my NFS setup performance wise, and seems stable despite warnings of high I/O causing VMWare to drop the LUN (I tested with bonnie++ as it seems this is an effective tool in getting the LUN to drop in VMWare).
Product Name: PERC 5/i Integrated
Memory: 256MB
BBU: Present ...
Default Cache Policy: WriteBack, ReadAheadNone, Direct, No Write Cache if Bad BBU
Current Cache Policy: WriteBack, ReadAheadNone, Direct, No Write Cache if Bad BBU
Access Policy: Read/Write
Disk Cache Policy: Disk's Default
On Wed, Feb 16, 2011 at 9:31 PM, James Chase james@wintercastle.net wrote:
Can anyone with write-back cache working just confirm that they see some sort of indication of write-back in dmesg?
I thought this thing is really masked from the OS and handled by the raid controller BIOS completely??
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Dominik Zyla -
Fajar Priyanto -
James Chase -
Scott Silva