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Defragmenting Mac RAID’s (Bob Z)
Bob Zelin,
It was nice to finally meet you at NAB this year!
We’re a post/broadcast video facility. We have a number of FCP stations that mainly digitize and master to tape uncompressed 8-bit HD. Some of these RAID’s that we digitize to are internal, some external. These RAID’s don’t necessitate sharing or anything, they’re just local arrays to each station that are workhorses – capture half a terabyte here, transfer to the client’s external drive, later delete half a terabyte, master it to tape, then delete, on to the next job, etc. Lots of FCP mastering to tape and data transfers on and off the RAID’s. The problem is that after a while (sometimes just a few weeks after wiping and rebuilding the RAID) despite the RAID disk speeds checking in at close to 400, they will still drop frames when playing out uncompressed 8-bit HD. Our guess is that the heavy amount of file transfers and deletions slowly fragment the drives. I’m interested if you know of any defragmenting solutions for Mac RAID’s as clearly OSX’s supposedly automatic defragmentation either sucks or probably was not designed to defrag such heavy amounts of data such as this. I hope your sitting down when you read this because it may come as a shock to you, but our Hitachi based RAID’s have not had this problem yet :). These RAID’s consist mostly of Western Digital drives.
We do understand that backing up whatever is needed once a month or so and then erasing all the drives and rebuilding the RAID’s is doable and has worked for us. Just wondering if you know of any solutions to maintaining cheap, fast, dirty local RAID’s such as this that handle a lot of data traffic.Thanks and like I said, get up here to Chicago and visit our facility. It’s just like Florida here in the summer except our ocean is a lake.
Chad Brewer
Senior Tape Operator/Engineer
TeleVersions -
8 Replies
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If you are wiping the drives, then maybe you could try to re-RAID the drives. There is no better “defragment” then rebuilding the parity from scratch 🙂
-Jordan
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After I`ve done a full reinstallation of software, sometimes I make a few folders and load a stack of DVDs in them with no intention of using them. Later when fragmentation bogs things down I empty the folders and use them or their space for work. This is no big trick but it does let me “lose some steam” at will if the fragmentation gets too bad.
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Erase and Re-RAID is what we have been doing and understand is the only option it seems for this type of work. Thank you Jordan and Fred for your input.
Chad Brewer
Senior Tape Operator/Engineer
TeleVersions -
I would opine that there is one more option. Backing up and restoring can be labor intensive, especially when something goes wrong.
You could also use a Defrag utility such as the one that is now in Drive Genius 3 or iDefrag for HFS formatted volumes. One of the keys in dealing with fragmentation is not only defragging your files, but also defragging the free space. These utilities do this.
In an XSAN environment, your only choice for proper defrag is the backup and restore process.
Jeff Bernstein
Digital Desktop Consulting
Apple Pro Video VAR
XSAN Certified
MetaSAN Master Reseller323-653-7611
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Thanks Jeff!
I had no idea about these Mac drive maintenance programs, but then again we all succumb to inadequate google searching from time to time. I will definitely check them out. Thanks again for your input. It helped me through Bob Zelin’s deafening silence 🙂 I’m on Bob’s blacklist already!Chad Brewer
Senior Tape Operator/Engineer
TeleVersions -
Don`t worry about the one- man blacklisting Chad, he`s only running after you with a paintbrush full of tar! Just wait until you have to sell all that extra programming you`re now making more efficiently. Programming sales consortiums anyone? 🙂 🙁 🙂
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Thanks Fred.
Why aren’t you using the avatar I Photoshopped for you? I thought it was cool.Chad Brewer
Senior Tape Operator/Engineer
TeleVersions -
Chad, I don`t have a clipper tool installed on any compu. I don`t have the avatar picture trimmed down to 72 x 72 pixels yet.
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