<?xml version="1.0" encoding="utf-8"?> <rss version="2.0" xml:base="http://www.technologicalwanderings.co.uk" xmlns:dc="http://purl.org/dc/elements/1.1/"> <channel> <title>Technological Wanderings - hdd</title> <link>http://www.technologicalwanderings.co.uk/taxonomy/term/76</link> <description></description> <language>en</language> <item> <title>Storage</title> <link>http://www.technologicalwanderings.co.uk/node/38</link> <description><div class="field field-name-taxonomy-vocabulary-1 field-type-taxonomy-term-reference field-label-above"><div class="field-label">Keywords:&nbsp;</div><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/28">backup</a></div><div class="field-item odd"><a href="/taxonomy/term/74">storage</a></div><div class="field-item even"><a href="/taxonomy/term/75">hard disk</a></div><div class="field-item odd"><a href="/taxonomy/term/76">hdd</a></div><div class="field-item even"><a href="/taxonomy/term/77">tape</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p>I am fascinated by storage on computers. The fact is, I'm fascinated by most things computing and storage is one of those things. Hard disks are noisy, slow and unreliable - yet still today the best mass storage devices we have. </p> <p>On my home network, incoming data from the Internet first hits my firewall machine. This has been upgraded many times using the spares from other machines, but the storage is a legacy dating back maybe 6 years. It's powered by a single 30GB disk. It's actually been replaced, and even the OS replaced, but as a spare parts machine replacements have never been at the same time: no co-ordinated upgrades. So this is an unRAIDed disk. To compensate, it's fully backed up and can be restored in entirety from tape. </p> <p>The firewall also runs CCTV and other odd security tasks - not all IP related. I have a pair of spare 120GB disks for it (30GB minus OS doesn't leave much room for video). Strangely these disks were once in the firewall as part of a RAID5 when I needed some extra PCI and IDE slots for a storage array, which was later moved to a more appropriate machine. </p> <p>The next machine is my primary server. This is by far the most interesting storage machine:<br /> 8 disks<br /> 3x RAID1 mirrors - /boot &amp; /, /home, music<br /> 1x RAID5 (4 disks) - everything else </p> <p>The first 1GB of the RAID5 disks are actually two RAID1s. That is, using Linux software raid I have the ability to use different levels of RAID on the same physical disks. The upper 300GB portions of the RAID5 disks are the RAID5 section. </p> <p>On top of the RAID5 is LVM. LVM is truly great. I have 400GB allocated to partitions - /var and /usr etc. 400GB is currently completely unallocated - if I need it for anything, I can bring it online at any moment, either in addition to existing partitions or as new partitions. If I ever run out of space, I can add more physical disks and extend the LVM onto them. </p> <p>Some of the RAID1 disks backup by replication onto a partition on the LVM. For this I use rsync run nightly in a small script, which also handles backing up and archival of databases. </p> <p>The root and boot partitions are not on LVM, as I followed general advice. If you lose the LVM for whatever reason, you want to be able to boot the machine to fix it. Especially if you don't have a CDROM drive in the machine to boot a rescue disk. </p> <p>Each disk in on it's own IDE channel. No slave disks - on IDE, if one disk fails, the other on the same cable will be lost too. I used to split RAID1 over channels - then a failure on one array kills another array. Not good for diagnosing it later. </p> <p>Moving on: my 1U server.<br /> This has a pair of 20GB disks, in a Linux RAID1. The machine has front access disks so you can remove them without disassembling the machine (and removing it from a rack - it's not on rails). However they are not hot-swap. It's IDE again. IDE is a very poor interface, but for decades the cheapest and most available. The machine has a BIOS based hard/software RAID. It's awful. It is supported only by Windows, FreeBSD and Linux 2.4, and to rebuild the array you have to drop down to the BIOS. </p> <p>On to my main desktop, one which isn't a Mac:<br /> One 160GB SATA2 disk. Almost empty as all storage is held on the server. There's a lot of temporary files on it and the OS though - the disk was chosen for speed and the size is a reflection of the best price point for a disk used for only temporary files.</p> <p>Further: Amiga 4000<br /> Two disks, a 40GB and a 4GB, both IDE. It was a 4 and 20GB but the 20GB developed 'noise' - it worked fine since 1999 until mid 2008, and still does, but it's loud. The Amiga runs 24h and needs to be quiet. So I replaced it with a silent 40GB and decided to get rid of the 4GB (dating from 1997). Bah, lots of work - the machine doesn't like the large disk. I used to run a 80GB on it but this is different somehow. So the 4GB boots the basic OS then reboots into a 40GB supporting version of the OS. </p> <p>Onwards: iMac<br /> 250GB SATA2, 3.5". Not interesting. Boots MacOS, works until it fails (no RAID in an iMac). Feels very fast. </p> <p>Onwards: MacBook<br /> 80GB SATA2, 2.5". Same, but is vastly slower than the iMac. the iMac has almost the same spec - same CPU, same memory - but the overall performance is completely different and pretty much entirely down to the disk. </p> <p>Onwards: Amiga 4000T<br /> 36GB and 9GB SCSI2-Ultrawide. Old, tried, tested, and as fast as some new IDE disks I've bought. IDE sucks. SCSI is good (except for the plethora of connectors which all do much the same thing - beyond physical connectors SCSI is almost completely forward and backward compatible). </p> <p>Boredom is hitting right now. Disks are disks and I have lots, so to continue on with something else...: </p> <p>Backups: DLT-7000 x2 drives, DLT-IV tapes, all in a robot tape changer unit with 32 tape cells.<br /> This is the coolest piece of hardware I have. A huge, power hungry Dell box (rebranded StorageTek, of course - do Dell make anything?). Lots of tapes. Terabytes of potential storage. Most importantly, a big robot arm that moves tapes around, loads and unloads the tape drives. Very cool to watch.</p> <p>It's connected to the primary server using high voltage differential SCSI (I didn't know this existed back when I bought the changer, it was called just 'differential SCSI' - cue lots of effort trying to get it working with LVD SCSI...). </p> <p>Amanda is the software I used to manage it. It does everything for me, now I have it set up. It did take a great deal of configuration though... I have it dump backups to a holding disk overnight on Friday and send it to tape on Saturday (switch on the unit, run the command on the server, wait for the notification that it has finished). </p> <p>I was hoping to write something interesting in this post. It seems that I haven't. I blame MIT and UC Berkeley, as I'm watching some of their physics lectures on YouTube while I (try to) write this.</p> </div></div></div></description> <pubDate>Sat, 26 Jul 2008 18:48:22 +0000</pubDate> <dc:creator>techuser</dc:creator> <guid isPermaLink="false">38 at http://www.technologicalwanderings.co.uk</guid> <comments>http://www.technologicalwanderings.co.uk/node/38#comments</comments> </item> </channel> </rss>