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Posts in Storage
Why partition X does not end on cylinder boundary warnings don't matter
While reviewing the partion layout on one of my hard drives, I noticed a number of "Partition X does not end on cylinder boundary" messages in the fdisk output: This was a bit disconcerting at first, but after a few minutes of thinking it dawned on me that modern systems use LBA (Logical Block Addressing) instead of CHS (Cylinder/Head/Sector) to address disk drives. If we view the partition table using sectors instead of cylinders: We can see that we end at a specific sector number, and start the next partition at that number plus one. I must say that I have grown quite fond of sfdisk and parted, and they sure make digging through DOS and GPT labels super easy.
$ read more →Better ZFS pool fault handling coming to an opensolaris release near you!
I just saw the following ARC case fly by, and this will be a welcome addition to the ZFS file system!: OVERVIEW: Uncooperative or deceptive hardware, combined with power failures or sudden lack of access to devices, can result in zpools without redundancy being non-importable. ZFS' copy-on-write and Merkle tree properties will sometimes allow us to recover from these problems. Only ad-hoc means currently exist to take advantage of this recoverability. This proposal aims to rectify that short-coming…
$ read more →Getting tape drive throughput and performance statistics on Linux hosts
I manager a number of Linux Netbackup media servers, and just recently learned that Linux doesn't provide a tool to view tape statistics (it appears there are no /proc interfaces to retrieve SCSI tape drive performance data). Fortunately the SystemTap developers saw this glaring deficiency, and created the iostat-scsi.stp script to display statistics for each SCSI tape and disk device in a server. To use SystemTap on a Redhat, CentOS or Fedora Linux host, you will first need to install the kernel debuginfo files. Here are the commands I used to install the debuginfo RPMs on a Redhat Enterprise Linux machine (you can download the RHEL debuginfo files from the Redhat FTP server, and you can get the debuginfo files for CentOS and Fedora from one of the various mirrors): Once the debuginfo files are installed, you can download the iostat-scsi.stp script from the systemtap website…
$ read more →Triple parity RAIDZ (RAIDZ3) support in ZFS
I just saw the following putback notice come over the wire: This is pretty sweet, and with the introduction of 2TB+ drives, using multiple parity drives will become essential to ensuring that your data is safe when a drive failures occur.
$ read more →Zoning Brocade switches Putting it all together
I wanted to conclude my Brocade zoning posts by discussing a couple of best practices. Two issues I have seen in the real world are inconsistent and non-descriptive names, and a lack of configuration backups. Using descriptive names such as "Fabric1Switch1Port8" or "AppServer1Port1" makes the output quite a bit more readable, which is extremely helpful when you are trying to gauge the impact of a faulty initiator or SFP at 3am. Backing up the configuration on a switch is super easy to do, and there are a number of tools available to automate this process (I have written pexpect scripts to do this)…
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