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 <title>Technological Wanderings - hdd</title>
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 <title>Storage</title>
 <link>http://www.technologicalwanderings.co.uk/node/38</link>
 <description>&lt;div class=&quot;field field-name-taxonomy-vocabulary-1 field-type-taxonomy-term-reference field-label-above&quot;&gt;&lt;div class=&quot;field-label&quot;&gt;Keywords:&amp;nbsp;&lt;/div&gt;&lt;div class=&quot;field-items&quot;&gt;&lt;div class=&quot;field-item even&quot;&gt;&lt;a href=&quot;/taxonomy/term/28&quot;&gt;backup&lt;/a&gt;&lt;/div&gt;&lt;div class=&quot;field-item odd&quot;&gt;&lt;a href=&quot;/taxonomy/term/74&quot;&gt;storage&lt;/a&gt;&lt;/div&gt;&lt;div class=&quot;field-item even&quot;&gt;&lt;a href=&quot;/taxonomy/term/75&quot;&gt;hard disk&lt;/a&gt;&lt;/div&gt;&lt;div class=&quot;field-item odd&quot;&gt;&lt;a href=&quot;/taxonomy/term/76&quot;&gt;hdd&lt;/a&gt;&lt;/div&gt;&lt;div class=&quot;field-item even&quot;&gt;&lt;a href=&quot;/taxonomy/term/77&quot;&gt;tape&lt;/a&gt;&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;&lt;div class=&quot;field field-name-body field-type-text-with-summary field-label-hidden&quot;&gt;&lt;div class=&quot;field-items&quot;&gt;&lt;div class=&quot;field-item even&quot;&gt;&lt;p&gt;I am fascinated by storage on computers. The fact is, I&#039;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. &lt;/p&gt;
&lt;p&gt;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&#039;s powered by a single 30GB disk. It&#039;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&#039;s fully backed up and can be restored in entirety from tape. &lt;/p&gt;
&lt;p&gt;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&#039;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. &lt;/p&gt;
&lt;p&gt;The next machine is my primary server. This is by far the most interesting storage machine:&lt;br /&gt;
8 disks&lt;br /&gt;
3x RAID1 mirrors - /boot &amp;amp; /,  /home, music&lt;br /&gt;
1x RAID5 (4 disks) - everything else &lt;/p&gt;
&lt;p&gt;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. &lt;/p&gt;
&lt;p&gt;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. &lt;/p&gt;
&lt;p&gt;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. &lt;/p&gt;
&lt;p&gt;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&#039;t have a CDROM drive in the machine to boot a rescue disk. &lt;/p&gt;
&lt;p&gt;Each disk in on it&#039;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. &lt;/p&gt;
&lt;p&gt;Moving on: my 1U server.&lt;br /&gt;
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&#039;s not on rails). However they are not hot-swap. It&#039;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&#039;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. &lt;/p&gt;
&lt;p&gt;On to my main desktop, one which isn&#039;t a Mac:&lt;br /&gt;
One 160GB SATA2 disk. Almost empty as all storage is held on the server. There&#039;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.&lt;/p&gt;
&lt;p&gt;Further: Amiga 4000&lt;br /&gt;
Two disks, a 40GB and a 4GB, both IDE. It was a 4 and 20GB but the 20GB developed &#039;noise&#039; - it worked fine since 1999 until mid 2008, and still does, but it&#039;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&#039;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. &lt;/p&gt;
&lt;p&gt;Onwards: iMac&lt;br /&gt;
250GB SATA2, 3.5&quot;. Not interesting. Boots MacOS, works until it fails (no RAID in an iMac). Feels very fast. &lt;/p&gt;
&lt;p&gt;Onwards: MacBook&lt;br /&gt;
80GB SATA2, 2.5&quot;. 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. &lt;/p&gt;
&lt;p&gt;Onwards: Amiga 4000T&lt;br /&gt;
36GB and 9GB SCSI2-Ultrawide. Old, tried, tested, and as fast as some new IDE disks I&#039;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). &lt;/p&gt;
&lt;p&gt;Boredom is hitting right now. Disks are disks and I have lots, so to continue on with something else...: &lt;/p&gt;
&lt;p&gt;Backups: DLT-7000 x2 drives, DLT-IV tapes, all in a robot tape changer unit with 32 tape cells.&lt;br /&gt;
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.&lt;/p&gt;
&lt;p&gt;It&#039;s connected to the primary server using high voltage differential SCSI (I didn&#039;t know this existed back when I bought the changer, it was called just &#039;differential SCSI&#039; - cue lots of effort trying to get it working with LVD SCSI...). &lt;/p&gt;
&lt;p&gt;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). &lt;/p&gt;
&lt;p&gt;I was hoping to write something interesting in this post. It seems that I haven&#039;t. I blame MIT and UC Berkeley, as I&#039;m watching some of their physics lectures on YouTube while I (try to) write this.&lt;/p&gt;
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 <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>
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