Recommend SSD's for ZFS array (one read cache & ZIL)

gbh · 10th May 2011, 11:49 PM

Recommendations greatly accepted:

I need the following:

1 x SSD (must be MLC) 40/60/80gig is fine, to be used for read cache (L2ARC)

and

1 x SSD (must be SLC, must have supercapacitor) smallest size possible
to be used for ZIL

grs1961 · 11th May 2011, 12:17 AM

Not going to recommend SSD's but just point out that you need two of each, you should mirror ZILs and ARCs, because when one fails everything stops until it is replaced (or the failure otherwise compensated for).

gbh · 11th May 2011, 12:23 AM

tx for reply
it's just for a simple test/lab machine, nothing critical or productional at this stage.
UPS will be on production machine eventually (yes I know this doesn't count for panic's etc)
8+(
pretty sure I cant afford battery backed ram either...

davros123 · 11th May 2011, 2:58 AM

Quote:

Originally Posted by grs1961

Not going to recommend SSD's but just point out that you need two of each, you should mirror ZILs and ARCs, because when one fails everything stops until it is replaced (or the failure otherwise compensated for).

you only need to mirror the zil, not the cache...and iirc, this is absolutely critical for the older versions of zfs...(pre 21?)...but less so for the newer zfs's where the the loss of a zil is not fatal for the pool, it is for the data it was writing, but not the pool....so depending upon the data you are writing, you may still want to mirror the zil, but definitely not the cache.

also, before you spend the $’s be sure to run the tests to verify you will get value from a zil and/or cache. your writes may bypass the zill...and the readsmay not be cached. you can do this without having a zil.

gbh · 11th May 2011, 4:38 PM

any thoughts on what hardware I should be using?
itchy to buy..

Dropbear · 11th May 2011, 5:01 PM

What Davros said.. if you're stuck at GbE speeds, you probably wont see a difference

10th May 2011, 11:49 PM	#1
gbh Member Join Date: Aug 2001 Location: Sydney Posts: 2,008	Recommend SSD's for ZFS array (one read cache & ZIL) Recommendations greatly accepted: I need the following: 1 x SSD (must be MLC) 40/60/80gig is fine, to be used for read cache (L2ARC) and 1 x SSD (must be SLC, must have supercapacitor) smallest size possible to be used for ZIL __________________ Trades: n00by, hikaru78, rdorman, axxian, VR4hore, hotmx83, bangmango plus about a million others that i have forgotten over the years.

11th May 2011, 12:23 AM	#3
gbh Member Join Date: Aug 2001 Location: Sydney Posts: 2,008	tx for reply it's just for a simple test/lab machine, nothing critical or productional at this stage. UPS will be on production machine eventually (yes I know this doesn't count for panic's etc) 8+( pretty sure I cant afford battery backed ram either... __________________ Trades: n00by, hikaru78, rdorman, axxian, VR4hore, hotmx83, bangmango plus about a million others that i have forgotten over the years.

11th May 2011, 4:38 PM	#5
gbh Member Join Date: Aug 2001 Location: Sydney Posts: 2,008	any thoughts on what hardware I should be using? itchy to buy.. __________________ Trades: n00by, hikaru78, rdorman, axxian, VR4hore, hotmx83, bangmango plus about a million others that i have forgotten over the years.

11th May 2011, 5:01 PM	#6
Dropbear Member Join Date: Jun 2001 Location: Brisbane Posts: 8,944	What Davros said.. if you're stuck at GbE speeds, you probably wont see a difference __________________ 500Px \| Model Mayhem \| Flickr \| DeviantArt

11th May 2011, 12:17 AM	#2
grs1961 Member Join Date: Jan 2005 Location: Melbourne Posts: 423	Not going to recommend SSD's but just point out that you need two of each, you should mirror ZILs and ARCs, because when one fails everything stops until it is replaced (or the failure otherwise compensated for).